/*
   *  linux/fs/proc/inode.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */
  
  #include <linux/time.h>
  #include <linux/proc_fs.h>
  #include <linux/kernel.h>

  #include <linux/pid_namespace.h>

  #include <linux/mm.h>
  #include <linux/string.h>
  #include <linux/stat.h>

  #include <linux/completion.h>

  #include <linux/poll.h>

  #include <linux/file.h>
  #include <linux/limits.h>
  #include <linux/init.h>
  #include <linux/module.h>

  #include <linux/sysctl.h>

  #include <linux/seq_file.h>

  #include <linux/slab.h>

  #include <linux/mount.h>

  
  #include <asm/system.h>
  #include <asm/uaccess.h>

  #include "internal.h"

  static void proc_evict_inode(struct inode *inode)

  {
  	struct proc_dir_entry *de;

  	struct ctl_table_header *head;

  	const struct proc_ns_operations *ns_ops;

  	truncate_inode_pages(&inode->i_data, 0);

  	end_writeback(inode);

  	/* Stop tracking associated processes */

  	put_pid(PROC_I(inode)->pid);

  
  	/* Let go of any associated proc directory entry */
  	de = PROC_I(inode)->pde;

  	if (de)

  		pde_put(de);

  	head = PROC_I(inode)->sysctl;
  	if (head) {
  		rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
  		sysctl_head_put(head);
  	}

  	/* Release any associated namespace */
  	ns_ops = PROC_I(inode)->ns_ops;
  	if (ns_ops && ns_ops->put)
  		ns_ops->put(PROC_I(inode)->ns);

  }

  static struct kmem_cache * proc_inode_cachep;

  
  static struct inode *proc_alloc_inode(struct super_block *sb)
  {
  	struct proc_inode *ei;
  	struct inode *inode;

  	ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);

  	if (!ei)
  		return NULL;

  	ei->pid = NULL;

  	ei->fd = 0;

  	ei->op.proc_get_link = NULL;
  	ei->pde = NULL;

  	ei->sysctl = NULL;
  	ei->sysctl_entry = NULL;

  	ei->ns = NULL;
  	ei->ns_ops = NULL;

  	inode = &ei->vfs_inode;
  	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  	return inode;
  }

  static void proc_i_callback(struct rcu_head *head)

  {

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

  	kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  }

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

  static void init_once(void *foo)

  {
  	struct proc_inode *ei = (struct proc_inode *) foo;

  	inode_init_once(&ei->vfs_inode);

  }

  void __init proc_init_inodecache(void)

  {
  	proc_inode_cachep = kmem_cache_create("proc_inode_cache",
  					     sizeof(struct proc_inode),

  					     0, (SLAB_RECLAIM_ACCOUNT|

  						SLAB_MEM_SPREAD|SLAB_PANIC),

  					     init_once);

  }

  static int proc_show_options(struct seq_file *seq, struct dentry *root)
  {

  	struct super_block *sb = root->d_sb;
  	struct pid_namespace *pid = sb->s_fs_info;
  
  	if (pid->pid_gid)
  		seq_printf(seq, ",gid=%lu", (unsigned long)pid->pid_gid);
  	if (pid->hide_pid != 0)
  		seq_printf(seq, ",hidepid=%u", pid->hide_pid);

  	return 0;
  }

  static const struct super_operations proc_sops = {

  	.alloc_inode	= proc_alloc_inode,
  	.destroy_inode	= proc_destroy_inode,

  	.drop_inode	= generic_delete_inode,

  	.evict_inode	= proc_evict_inode,

  	.statfs		= simple_statfs,

  	.remount_fs	= proc_remount,
  	.show_options	= proc_show_options,

  };

  static void __pde_users_dec(struct proc_dir_entry *pde)

  {

  	pde->pde_users--;
  	if (pde->pde_unload_completion && pde->pde_users == 0)
  		complete(pde->pde_unload_completion);

  }

  void pde_users_dec(struct proc_dir_entry *pde)

  {
  	spin_lock(&pde->pde_unload_lock);
  	__pde_users_dec(pde);

  	spin_unlock(&pde->pde_unload_lock);
  }
  
  static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
  {
  	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
  	loff_t rv = -EINVAL;
  	loff_t (*llseek)(struct file *, loff_t, int);
  
  	spin_lock(&pde->pde_unload_lock);
  	/*
  	 * remove_proc_entry() is going to delete PDE (as part of module
  	 * cleanup sequence). No new callers into module allowed.
  	 */
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);
  		return rv;
  	}
  	/*
  	 * Bump refcount so that remove_proc_entry will wail for ->llseek to
  	 * complete.
  	 */
  	pde->pde_users++;
  	/*
  	 * Save function pointer under lock, to protect against ->proc_fops
  	 * NULL'ifying right after ->pde_unload_lock is dropped.
  	 */
  	llseek = pde->proc_fops->llseek;
  	spin_unlock(&pde->pde_unload_lock);
  
  	if (!llseek)
  		llseek = default_llseek;
  	rv = llseek(file, offset, whence);
  
  	pde_users_dec(pde);
  	return rv;
  }
  
  static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  {
  	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
  	ssize_t rv = -EIO;
  	ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
  
  	spin_lock(&pde->pde_unload_lock);
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);
  		return rv;
  	}
  	pde->pde_users++;
  	read = pde->proc_fops->read;
  	spin_unlock(&pde->pde_unload_lock);
  
  	if (read)
  		rv = read(file, buf, count, ppos);
  
  	pde_users_dec(pde);
  	return rv;
  }
  
  static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
  {
  	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
  	ssize_t rv = -EIO;
  	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
  
  	spin_lock(&pde->pde_unload_lock);
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);
  		return rv;
  	}
  	pde->pde_users++;
  	write = pde->proc_fops->write;
  	spin_unlock(&pde->pde_unload_lock);
  
  	if (write)
  		rv = write(file, buf, count, ppos);
  
  	pde_users_dec(pde);
  	return rv;
  }
  
  static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
  {
  	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);

  	unsigned int rv = DEFAULT_POLLMASK;

  	unsigned int (*poll)(struct file *, struct poll_table_struct *);
  
  	spin_lock(&pde->pde_unload_lock);
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);
  		return rv;
  	}
  	pde->pde_users++;
  	poll = pde->proc_fops->poll;
  	spin_unlock(&pde->pde_unload_lock);
  
  	if (poll)
  		rv = poll(file, pts);
  
  	pde_users_dec(pde);
  	return rv;
  }
  
  static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
  	long rv = -ENOTTY;

  	long (*ioctl)(struct file *, unsigned int, unsigned long);

  
  	spin_lock(&pde->pde_unload_lock);
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);
  		return rv;
  	}
  	pde->pde_users++;

  	ioctl = pde->proc_fops->unlocked_ioctl;

  	spin_unlock(&pde->pde_unload_lock);

  	if (ioctl)
  		rv = ioctl(file, cmd, arg);

  
  	pde_users_dec(pde);
  	return rv;
  }
  
  #ifdef CONFIG_COMPAT
  static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
  	long rv = -ENOTTY;
  	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
  
  	spin_lock(&pde->pde_unload_lock);
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);
  		return rv;
  	}
  	pde->pde_users++;
  	compat_ioctl = pde->proc_fops->compat_ioctl;
  	spin_unlock(&pde->pde_unload_lock);
  
  	if (compat_ioctl)
  		rv = compat_ioctl(file, cmd, arg);
  
  	pde_users_dec(pde);
  	return rv;
  }
  #endif
  
  static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
  	int rv = -EIO;
  	int (*mmap)(struct file *, struct vm_area_struct *);
  
  	spin_lock(&pde->pde_unload_lock);
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);
  		return rv;
  	}
  	pde->pde_users++;
  	mmap = pde->proc_fops->mmap;
  	spin_unlock(&pde->pde_unload_lock);
  
  	if (mmap)
  		rv = mmap(file, vma);
  
  	pde_users_dec(pde);
  	return rv;
  }
  
  static int proc_reg_open(struct inode *inode, struct file *file)
  {
  	struct proc_dir_entry *pde = PDE(inode);
  	int rv = 0;
  	int (*open)(struct inode *, struct file *);

  	int (*release)(struct inode *, struct file *);
  	struct pde_opener *pdeo;
  
  	/*
  	 * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
  	 * sequence. ->release won't be called because ->proc_fops will be
  	 * cleared. Depending on complexity of ->release, consequences vary.
  	 *
  	 * We can't wait for mercy when close will be done for real, it's
  	 * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
  	 * by hand in remove_proc_entry(). For this, save opener's credentials
  	 * for later.
  	 */
  	pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
  	if (!pdeo)
  		return -ENOMEM;

  
  	spin_lock(&pde->pde_unload_lock);
  	if (!pde->proc_fops) {
  		spin_unlock(&pde->pde_unload_lock);

  		kfree(pdeo);

  		return -ENOENT;

  	}
  	pde->pde_users++;
  	open = pde->proc_fops->open;

  	release = pde->proc_fops->release;

  	spin_unlock(&pde->pde_unload_lock);
  
  	if (open)
  		rv = open(inode, file);

  	spin_lock(&pde->pde_unload_lock);
  	if (rv == 0 && release) {
  		/* To know what to release. */
  		pdeo->inode = inode;
  		pdeo->file = file;
  		/* Strictly for "too late" ->release in proc_reg_release(). */
  		pdeo->release = release;
  		list_add(&pdeo->lh, &pde->pde_openers);
  	} else
  		kfree(pdeo);
  	__pde_users_dec(pde);
  	spin_unlock(&pde->pde_unload_lock);

  	return rv;
  }

  static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
  					struct inode *inode, struct file *file)
  {
  	struct pde_opener *pdeo;
  
  	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
  		if (pdeo->inode == inode && pdeo->file == file)
  			return pdeo;
  	}
  	return NULL;
  }

  static int proc_reg_release(struct inode *inode, struct file *file)
  {
  	struct proc_dir_entry *pde = PDE(inode);
  	int rv = 0;
  	int (*release)(struct inode *, struct file *);

  	struct pde_opener *pdeo;

  
  	spin_lock(&pde->pde_unload_lock);

  	pdeo = find_pde_opener(pde, inode, file);

  	if (!pde->proc_fops) {

  		/*
  		 * Can't simply exit, __fput() will think that everything is OK,
  		 * and move on to freeing struct file. remove_proc_entry() will
  		 * find slacker in opener's list and will try to do non-trivial
  		 * things with struct file. Therefore, remove opener from list.
  		 *
  		 * But if opener is removed from list, who will ->release it?
  		 */
  		if (pdeo) {
  			list_del(&pdeo->lh);
  			spin_unlock(&pde->pde_unload_lock);
  			rv = pdeo->release(inode, file);
  			kfree(pdeo);
  		} else
  			spin_unlock(&pde->pde_unload_lock);

  		return rv;
  	}
  	pde->pde_users++;
  	release = pde->proc_fops->release;

  	if (pdeo) {
  		list_del(&pdeo->lh);
  		kfree(pdeo);
  	}

  	spin_unlock(&pde->pde_unload_lock);
  
  	if (release)
  		rv = release(inode, file);
  
  	pde_users_dec(pde);
  	return rv;
  }
  
  static const struct file_operations proc_reg_file_ops = {
  	.llseek		= proc_reg_llseek,
  	.read		= proc_reg_read,
  	.write		= proc_reg_write,
  	.poll		= proc_reg_poll,
  	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl	= proc_reg_compat_ioctl,
  #endif
  	.mmap		= proc_reg_mmap,
  	.open		= proc_reg_open,
  	.release	= proc_reg_release,
  };

  #ifdef CONFIG_COMPAT
  static const struct file_operations proc_reg_file_ops_no_compat = {
  	.llseek		= proc_reg_llseek,
  	.read		= proc_reg_read,
  	.write		= proc_reg_write,
  	.poll		= proc_reg_poll,
  	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
  	.mmap		= proc_reg_mmap,
  	.open		= proc_reg_open,
  	.release	= proc_reg_release,
  };
  #endif

  struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)

  {
  	struct inode * inode;

  	inode = iget_locked(sb, de->low_ino);

  	if (!inode)

  		return NULL;

  	if (inode->i_state & I_NEW) {
  		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  		PROC_I(inode)->fd = 0;
  		PROC_I(inode)->pde = de;

  
  		if (de->mode) {
  			inode->i_mode = de->mode;
  			inode->i_uid = de->uid;
  			inode->i_gid = de->gid;
  		}
  		if (de->size)
  			inode->i_size = de->size;
  		if (de->nlink)

  			set_nlink(inode, de->nlink);

  		if (de->proc_iops)
  			inode->i_op = de->proc_iops;
  		if (de->proc_fops) {
  			if (S_ISREG(inode->i_mode)) {

  #ifdef CONFIG_COMPAT

  				if (!de->proc_fops->compat_ioctl)
  					inode->i_fop =
  						&proc_reg_file_ops_no_compat;
  				else

  #endif

  					inode->i_fop = &proc_reg_file_ops;
  			} else {
  				inode->i_fop = de->proc_fops;

  			}

  		}

  		unlock_new_inode(inode);

  	} else

  	       pde_put(de);

  	return inode;

  }			

  int proc_fill_super(struct super_block *s)

  {
  	struct inode * root_inode;

  	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;

  	s->s_blocksize = 1024;
  	s->s_blocksize_bits = 10;
  	s->s_magic = PROC_SUPER_MAGIC;
  	s->s_op = &proc_sops;
  	s->s_time_gran = 1;
  	

  	pde_get(&proc_root);

  	root_inode = proc_get_inode(s, &proc_root);

  	if (!root_inode)
  		goto out_no_root;

  	root_inode->i_uid = 0;
  	root_inode->i_gid = 0;
  	s->s_root = d_alloc_root(root_inode);
  	if (!s->s_root)
  		goto out_no_root;
  	return 0;
  
  out_no_root:
  	printk("proc_read_super: get root inode failed
  ");
  	iput(root_inode);

  	pde_put(&proc_root);

  	return -ENOMEM;
  }