/*
   * proc/fs/generic.c --- generic routines for the proc-fs
   *
   * This file contains generic proc-fs routines for handling
   * directories and files.
   * 
   * Copyright (C) 1991, 1992 Linus Torvalds.
   * Copyright (C) 1997 Theodore Ts'o
   */
  
  #include <linux/errno.h>
  #include <linux/time.h>
  #include <linux/proc_fs.h>
  #include <linux/stat.h>
  #include <linux/mm.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/printk.h>
  #include <linux/mount.h>
  #include <linux/init.h>
  #include <linux/idr.h>
  #include <linux/bitops.h>
  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <asm/uaccess.h>
  
  #include "internal.h"
  
  static DEFINE_RWLOCK(proc_subdir_lock);
  
  static int proc_match(unsigned int len, const char *name, struct proc_dir_entry *de)
  {
  	if (len < de->namelen)
  		return -1;
  	if (len > de->namelen)
  		return 1;
  
  	return memcmp(name, de->name, len);
  }
  
  static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)
  {
  	return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,
  			     subdir_node);
  }
  
  static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
  {
  	return rb_entry_safe(rb_next(&dir->subdir_node), struct proc_dir_entry,
  			     subdir_node);
  }
  
  static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,
  					      const char *name,
  					      unsigned int len)
  {
  	struct rb_node *node = dir->subdir.rb_node;
  
  	while (node) {
  		struct proc_dir_entry *de = container_of(node,
  							 struct proc_dir_entry,
  							 subdir_node);
  		int result = proc_match(len, name, de);
  
  		if (result < 0)
  			node = node->rb_left;
  		else if (result > 0)
  			node = node->rb_right;
  		else
  			return de;
  	}
  	return NULL;
  }
  
  static bool pde_subdir_insert(struct proc_dir_entry *dir,
  			      struct proc_dir_entry *de)
  {
  	struct rb_root *root = &dir->subdir;
  	struct rb_node **new = &root->rb_node, *parent = NULL;
  
  	/* Figure out where to put new node */
  	while (*new) {
  		struct proc_dir_entry *this =
  			container_of(*new, struct proc_dir_entry, subdir_node);
  		int result = proc_match(de->namelen, de->name, this);
  
  		parent = *new;
  		if (result < 0)
  			new = &(*new)->rb_left;
  		else if (result > 0)
  			new = &(*new)->rb_right;
  		else
  			return false;
  	}
  
  	/* Add new node and rebalance tree. */
  	rb_link_node(&de->subdir_node, parent, new);
  	rb_insert_color(&de->subdir_node, root);
  	return true;
  }
  
  static int proc_notify_change(struct dentry *dentry, struct iattr *iattr)
  {
  	struct inode *inode = d_inode(dentry);
  	struct proc_dir_entry *de = PDE(inode);
  	int error;
  
  	error = inode_change_ok(inode, iattr);
  	if (error)
  		return error;
  
  	setattr_copy(inode, iattr);
  	mark_inode_dirty(inode);
  
  	proc_set_user(de, inode->i_uid, inode->i_gid);
  	de->mode = inode->i_mode;
  	return 0;
  }
  
  static int proc_getattr(struct vfsmount *mnt, struct dentry *dentry,
  			struct kstat *stat)
  {
  	struct inode *inode = d_inode(dentry);
  	struct proc_dir_entry *de = PDE(inode);
  	if (de && de->nlink)
  		set_nlink(inode, de->nlink);
  
  	generic_fillattr(inode, stat);
  	return 0;
  }
  
  static const struct inode_operations proc_file_inode_operations = {
  	.setattr	= proc_notify_change,
  };
  
  /*
   * This function parses a name such as "tty/driver/serial", and
   * returns the struct proc_dir_entry for "/proc/tty/driver", and
   * returns "serial" in residual.
   */
  static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
  			     const char **residual)
  {
  	const char     		*cp = name, *next;
  	struct proc_dir_entry	*de;
  	unsigned int		len;
  
  	de = *ret;
  	if (!de)
  		de = &proc_root;
  
  	while (1) {
  		next = strchr(cp, '/');
  		if (!next)
  			break;
  
  		len = next - cp;
  		de = pde_subdir_find(de, cp, len);
  		if (!de) {
  			WARN(1, "name '%s'
  ", name);
  			return -ENOENT;
  		}
  		cp += len + 1;
  	}
  	*residual = cp;
  	*ret = de;
  	return 0;
  }
  
  static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
  			   const char **residual)
  {
  	int rv;
  
  	read_lock(&proc_subdir_lock);
  	rv = __xlate_proc_name(name, ret, residual);
  	read_unlock(&proc_subdir_lock);
  	return rv;
  }
  
  static DEFINE_IDA(proc_inum_ida);
  static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */
  
  #define PROC_DYNAMIC_FIRST 0xF0000000U
  
  /*
   * Return an inode number between PROC_DYNAMIC_FIRST and
   * 0xffffffff, or zero on failure.
   */
  int proc_alloc_inum(unsigned int *inum)
  {
  	unsigned int i;
  	int error;
  
  retry:
  	if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL))
  		return -ENOMEM;
  
  	spin_lock_irq(&proc_inum_lock);
  	error = ida_get_new(&proc_inum_ida, &i);
  	spin_unlock_irq(&proc_inum_lock);
  	if (error == -EAGAIN)
  		goto retry;
  	else if (error)
  		return error;
  
  	if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
  		spin_lock_irq(&proc_inum_lock);
  		ida_remove(&proc_inum_ida, i);
  		spin_unlock_irq(&proc_inum_lock);
  		return -ENOSPC;
  	}
  	*inum = PROC_DYNAMIC_FIRST + i;
  	return 0;
  }
  
  void proc_free_inum(unsigned int inum)
  {
  	unsigned long flags;
  	spin_lock_irqsave(&proc_inum_lock, flags);
  	ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
  	spin_unlock_irqrestore(&proc_inum_lock, flags);
  }
  
  /*
   * Don't create negative dentries here, return -ENOENT by hand
   * instead.
   */
  struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
  		struct dentry *dentry)
  {
  	struct inode *inode;
  
  	read_lock(&proc_subdir_lock);
  	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
  	if (de) {
  		pde_get(de);
  		read_unlock(&proc_subdir_lock);
  		inode = proc_get_inode(dir->i_sb, de);
  		if (!inode)
  			return ERR_PTR(-ENOMEM);
  		d_set_d_op(dentry, &simple_dentry_operations);
  		d_add(dentry, inode);
  		return NULL;
  	}
  	read_unlock(&proc_subdir_lock);
  	return ERR_PTR(-ENOENT);
  }
  
  struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
  		unsigned int flags)
  {
  	return proc_lookup_de(PDE(dir), dir, dentry);
  }
  
  /*
   * This returns non-zero if at EOF, so that the /proc
   * root directory can use this and check if it should
   * continue with the <pid> entries..
   *
   * Note that the VFS-layer doesn't care about the return
   * value of the readdir() call, as long as it's non-negative
   * for success..
   */
  int proc_readdir_de(struct proc_dir_entry *de, struct file *file,
  		    struct dir_context *ctx)
  {
  	int i;
  
  	if (!dir_emit_dots(file, ctx))
  		return 0;
  
  	read_lock(&proc_subdir_lock);
  	de = pde_subdir_first(de);
  	i = ctx->pos - 2;
  	for (;;) {
  		if (!de) {
  			read_unlock(&proc_subdir_lock);
  			return 0;
  		}
  		if (!i)
  			break;
  		de = pde_subdir_next(de);
  		i--;
  	}
  
  	do {
  		struct proc_dir_entry *next;
  		pde_get(de);
  		read_unlock(&proc_subdir_lock);
  		if (!dir_emit(ctx, de->name, de->namelen,
  			    de->low_ino, de->mode >> 12)) {
  			pde_put(de);
  			return 0;
  		}
  		read_lock(&proc_subdir_lock);
  		ctx->pos++;
  		next = pde_subdir_next(de);
  		pde_put(de);
  		de = next;
  	} while (de);
  	read_unlock(&proc_subdir_lock);
  	return 1;
  }
  
  int proc_readdir(struct file *file, struct dir_context *ctx)
  {
  	struct inode *inode = file_inode(file);
  
  	return proc_readdir_de(PDE(inode), file, ctx);
  }
  
  /*
   * These are the generic /proc directory operations. They
   * use the in-memory "struct proc_dir_entry" tree to parse
   * the /proc directory.
   */
  static const struct file_operations proc_dir_operations = {
  	.llseek			= generic_file_llseek,
  	.read			= generic_read_dir,
  	.iterate		= proc_readdir,
  };
  
  /*
   * proc directories can do almost nothing..
   */
  static const struct inode_operations proc_dir_inode_operations = {
  	.lookup		= proc_lookup,
  	.getattr	= proc_getattr,
  	.setattr	= proc_notify_change,
  };
  
  static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)
  {
  	int ret;
  
  	ret = proc_alloc_inum(&dp->low_ino);
  	if (ret)
  		return ret;
  
  	write_lock(&proc_subdir_lock);
  	dp->parent = dir;
  	if (pde_subdir_insert(dir, dp) == false) {
  		WARN(1, "proc_dir_entry '%s/%s' already registered
  ",
  		     dir->name, dp->name);
  		write_unlock(&proc_subdir_lock);
  		proc_free_inum(dp->low_ino);
  		return -EEXIST;
  	}
  	write_unlock(&proc_subdir_lock);
  
  	return 0;
  }
  
  static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
  					  const char *name,
  					  umode_t mode,
  					  nlink_t nlink)
  {
  	struct proc_dir_entry *ent = NULL;
  	const char *fn;
  	struct qstr qstr;
  
  	if (xlate_proc_name(name, parent, &fn) != 0)
  		goto out;
  	qstr.name = fn;
  	qstr.len = strlen(fn);
  	if (qstr.len == 0 || qstr.len >= 256) {
  		WARN(1, "name len %u
  ", qstr.len);
  		return NULL;
  	}
  	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
  		WARN(1, "create '/proc/%s' by hand
  ", qstr.name);
  		return NULL;
  	}
  	if (is_empty_pde(*parent)) {
  		WARN(1, "attempt to add to permanently empty directory");
  		return NULL;
  	}
  
  	ent = kzalloc(sizeof(struct proc_dir_entry) + qstr.len + 1, GFP_KERNEL);
  	if (!ent)
  		goto out;
  
  	memcpy(ent->name, fn, qstr.len + 1);
  	ent->namelen = qstr.len;
  	ent->mode = mode;
  	ent->nlink = nlink;
  	ent->subdir = RB_ROOT;
  	atomic_set(&ent->count, 1);
  	spin_lock_init(&ent->pde_unload_lock);
  	INIT_LIST_HEAD(&ent->pde_openers);
  out:
  	return ent;
  }
  
  struct proc_dir_entry *proc_symlink(const char *name,
  		struct proc_dir_entry *parent, const char *dest)
  {
  	struct proc_dir_entry *ent;
  
  	ent = __proc_create(&parent, name,
  			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
  
  	if (ent) {
  		ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
  		if (ent->data) {
  			strcpy((char*)ent->data,dest);
  			ent->proc_iops = &proc_link_inode_operations;
  			if (proc_register(parent, ent) < 0) {
  				kfree(ent->data);
  				kfree(ent);
  				ent = NULL;
  			}
  		} else {
  			kfree(ent);
  			ent = NULL;
  		}
  	}
  	return ent;
  }
  EXPORT_SYMBOL(proc_symlink);
  
  struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
  		struct proc_dir_entry *parent, void *data)
  {
  	struct proc_dir_entry *ent;
  
  	if (mode == 0)
  		mode = S_IRUGO | S_IXUGO;
  
  	ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
  	if (ent) {
  		ent->data = data;
  		ent->proc_fops = &proc_dir_operations;
  		ent->proc_iops = &proc_dir_inode_operations;
  		parent->nlink++;
  		if (proc_register(parent, ent) < 0) {
  			kfree(ent);
  			parent->nlink--;
  			ent = NULL;
  		}
  	}
  	return ent;
  }
  EXPORT_SYMBOL_GPL(proc_mkdir_data);
  
  struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
  				       struct proc_dir_entry *parent)
  {
  	return proc_mkdir_data(name, mode, parent, NULL);
  }
  EXPORT_SYMBOL(proc_mkdir_mode);
  
  struct proc_dir_entry *proc_mkdir(const char *name,
  		struct proc_dir_entry *parent)
  {
  	return proc_mkdir_data(name, 0, parent, NULL);
  }
  EXPORT_SYMBOL(proc_mkdir);
  
  struct proc_dir_entry *proc_create_mount_point(const char *name)
  {
  	umode_t mode = S_IFDIR | S_IRUGO | S_IXUGO;
  	struct proc_dir_entry *ent, *parent = NULL;
  
  	ent = __proc_create(&parent, name, mode, 2);
  	if (ent) {
  		ent->data = NULL;
  		ent->proc_fops = NULL;
  		ent->proc_iops = NULL;
  		if (proc_register(parent, ent) < 0) {
  			kfree(ent);
  			parent->nlink--;
  			ent = NULL;
  		}
  	}
  	return ent;
  }
  
  struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
  					struct proc_dir_entry *parent,
  					const struct file_operations *proc_fops,
  					void *data)
  {
  	struct proc_dir_entry *pde;
  	if ((mode & S_IFMT) == 0)
  		mode |= S_IFREG;
  
  	if (!S_ISREG(mode)) {
  		WARN_ON(1);	/* use proc_mkdir() */
  		return NULL;
  	}
  
  	BUG_ON(proc_fops == NULL);
  
  	if ((mode & S_IALLUGO) == 0)
  		mode |= S_IRUGO;
  	pde = __proc_create(&parent, name, mode, 1);
  	if (!pde)
  		goto out;
  	pde->proc_fops = proc_fops;
  	pde->data = data;
  	pde->proc_iops = &proc_file_inode_operations;
  	if (proc_register(parent, pde) < 0)
  		goto out_free;
  	return pde;
  out_free:
  	kfree(pde);
  out:
  	return NULL;
  }
  EXPORT_SYMBOL(proc_create_data);
   
  void proc_set_size(struct proc_dir_entry *de, loff_t size)
  {
  	de->size = size;
  }
  EXPORT_SYMBOL(proc_set_size);
  
  void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
  {
  	de->uid = uid;
  	de->gid = gid;
  }
  EXPORT_SYMBOL(proc_set_user);
  
  static void free_proc_entry(struct proc_dir_entry *de)
  {
  	proc_free_inum(de->low_ino);
  
  	if (S_ISLNK(de->mode))
  		kfree(de->data);
  	kfree(de);
  }
  
  void pde_put(struct proc_dir_entry *pde)
  {
  	if (atomic_dec_and_test(&pde->count))
  		free_proc_entry(pde);
  }
  
  /*
   * Remove a /proc entry and free it if it's not currently in use.
   */
  void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
  {
  	struct proc_dir_entry *de = NULL;
  	const char *fn = name;
  	unsigned int len;
  
  	write_lock(&proc_subdir_lock);
  	if (__xlate_proc_name(name, &parent, &fn) != 0) {
  		write_unlock(&proc_subdir_lock);
  		return;
  	}
  	len = strlen(fn);
  
  	de = pde_subdir_find(parent, fn, len);
  	if (de)
  		rb_erase(&de->subdir_node, &parent->subdir);
  	write_unlock(&proc_subdir_lock);
  	if (!de) {
  		WARN(1, "name '%s'
  ", name);
  		return;
  	}
  
  	proc_entry_rundown(de);
  
  	if (S_ISDIR(de->mode))
  		parent->nlink--;
  	de->nlink = 0;
  	WARN(pde_subdir_first(de),
  	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'
  ",
  	     __func__, de->parent->name, de->name, pde_subdir_first(de)->name);
  	pde_put(de);
  }
  EXPORT_SYMBOL(remove_proc_entry);
  
  int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
  {
  	struct proc_dir_entry *root = NULL, *de, *next;
  	const char *fn = name;
  	unsigned int len;
  
  	write_lock(&proc_subdir_lock);
  	if (__xlate_proc_name(name, &parent, &fn) != 0) {
  		write_unlock(&proc_subdir_lock);
  		return -ENOENT;
  	}
  	len = strlen(fn);
  
  	root = pde_subdir_find(parent, fn, len);
  	if (!root) {
  		write_unlock(&proc_subdir_lock);
  		return -ENOENT;
  	}
  	rb_erase(&root->subdir_node, &parent->subdir);
  
  	de = root;
  	while (1) {
  		next = pde_subdir_first(de);
  		if (next) {
  			rb_erase(&next->subdir_node, &de->subdir);
  			de = next;
  			continue;
  		}
  		write_unlock(&proc_subdir_lock);
  
  		proc_entry_rundown(de);
  		next = de->parent;
  		if (S_ISDIR(de->mode))
  			next->nlink--;
  		de->nlink = 0;
  		if (de == root)
  			break;
  		pde_put(de);
  
  		write_lock(&proc_subdir_lock);
  		de = next;
  	}
  	pde_put(root);
  	return 0;
  }
  EXPORT_SYMBOL(remove_proc_subtree);
  
  void *proc_get_parent_data(const struct inode *inode)
  {
  	struct proc_dir_entry *de = PDE(inode);
  	return de->parent->data;
  }
  EXPORT_SYMBOL_GPL(proc_get_parent_data);
  
  void proc_remove(struct proc_dir_entry *de)
  {
  	if (de)
  		remove_proc_subtree(de->name, de->parent);
  }
  EXPORT_SYMBOL(proc_remove);
  
  void *PDE_DATA(const struct inode *inode)
  {
  	return __PDE_DATA(inode);
  }
  EXPORT_SYMBOL(PDE_DATA);