/*
   *  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/printk.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 <linux/magic.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;

  	truncate_inode_pages_final(&inode->i_data);

  	clear_inode(inode);

  	/* Stop tracking associated processes */

  	put_pid(PROC_I(inode)->pid);

  
  	/* Let go of any associated proc directory entry */

  	de = PDE(inode);

  	if (de)

  		pde_put(de);

  	head = PROC_I(inode)->sysctl;
  	if (head) {

  		RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);

  		sysctl_head_put(head);
  	}

  }

  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_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_ACCOUNT|
  						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 (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
  		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, 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,

  };

  enum {BIAS = -1U<<31};
  
  static inline int use_pde(struct proc_dir_entry *pde)
  {

  	return atomic_inc_unless_negative(&pde->in_use);

  }

  static void unuse_pde(struct proc_dir_entry *pde)

  {

  	if (atomic_dec_return(&pde->in_use) == BIAS)
  		complete(pde->pde_unload_completion);

  }

  /* pde is locked */
  static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
  {

  	if (pdeo->closing) {

  		/* somebody else is doing that, just wait */

  		DECLARE_COMPLETION_ONSTACK(c);
  		pdeo->c = &c;

  		spin_unlock(&pde->pde_unload_lock);

  		wait_for_completion(&c);

  		spin_lock(&pde->pde_unload_lock);

  	} else {
  		struct file *file;

  		pdeo->closing = 1;

  		spin_unlock(&pde->pde_unload_lock);
  		file = pdeo->file;
  		pde->proc_fops->release(file_inode(file), file);
  		spin_lock(&pde->pde_unload_lock);
  		list_del_init(&pdeo->lh);

  		if (pdeo->c)
  			complete(pdeo->c);

  		kfree(pdeo);

  	}

  }

  void proc_entry_rundown(struct proc_dir_entry *de)

  {

  	DECLARE_COMPLETION_ONSTACK(c);

  	/* Wait until all existing callers into module are done. */

  	de->pde_unload_completion = &c;
  	if (atomic_add_return(BIAS, &de->in_use) != BIAS)
  		wait_for_completion(&c);

  	spin_lock(&de->pde_unload_lock);

  	while (!list_empty(&de->pde_openers)) {
  		struct pde_opener *pdeo;

  		pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);

  		close_pdeo(de, pdeo);

  	}
  	spin_unlock(&de->pde_unload_lock);

  }

  static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
  {
  	struct proc_dir_entry *pde = PDE(file_inode(file));
  	loff_t rv = -EINVAL;
  	if (use_pde(pde)) {
  		loff_t (*llseek)(struct file *, loff_t, int);
  		llseek = pde->proc_fops->llseek;
  		if (!llseek)
  			llseek = default_llseek;
  		rv = llseek(file, offset, whence);
  		unuse_pde(pde);
  	}

  	return rv;
  }

  static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)

  {

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

  	struct proc_dir_entry *pde = PDE(file_inode(file));

  	ssize_t rv = -EIO;

  	if (use_pde(pde)) {
  		read = pde->proc_fops->read;
  		if (read)
  			rv = read(file, buf, count, ppos);
  		unuse_pde(pde);

  	}

  	return rv;
  }

  static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
  {
  	ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
  	struct proc_dir_entry *pde = PDE(file_inode(file));
  	ssize_t rv = -EIO;
  	if (use_pde(pde)) {
  		write = pde->proc_fops->write;
  		if (write)
  			rv = write(file, buf, count, ppos);
  		unuse_pde(pde);
  	}

  	return rv;
  }
  
  static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
  {

  	struct proc_dir_entry *pde = PDE(file_inode(file));

  	unsigned int rv = DEFAULT_POLLMASK;

  	unsigned int (*poll)(struct file *, struct poll_table_struct *);

  	if (use_pde(pde)) {
  		poll = pde->proc_fops->poll;
  		if (poll)
  			rv = poll(file, pts);
  		unuse_pde(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_inode(file));

  	long rv = -ENOTTY;

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

  	if (use_pde(pde)) {
  		ioctl = pde->proc_fops->unlocked_ioctl;
  		if (ioctl)
  			rv = ioctl(file, cmd, arg);
  		unuse_pde(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_inode(file));

  	long rv = -ENOTTY;
  	long (*compat_ioctl)(struct file *, unsigned int, unsigned long);

  	if (use_pde(pde)) {
  		compat_ioctl = pde->proc_fops->compat_ioctl;
  		if (compat_ioctl)
  			rv = compat_ioctl(file, cmd, arg);
  		unuse_pde(pde);

  	}

  	return rv;
  }
  #endif
  
  static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
  {

  	struct proc_dir_entry *pde = PDE(file_inode(file));

  	int rv = -EIO;
  	int (*mmap)(struct file *, struct vm_area_struct *);

  	if (use_pde(pde)) {
  		mmap = pde->proc_fops->mmap;
  		if (mmap)
  			rv = mmap(file, vma);
  		unuse_pde(pde);

  	}

  	return rv;
  }

  static unsigned long
  proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
  			   unsigned long len, unsigned long pgoff,
  			   unsigned long flags)

  {
  	struct proc_dir_entry *pde = PDE(file_inode(file));

  	unsigned long rv = -EIO;

  	if (use_pde(pde)) {

  		typeof(proc_reg_get_unmapped_area) *get_area;
  
  		get_area = pde->proc_fops->get_unmapped_area;

  #ifdef CONFIG_MMU

  		if (!get_area)
  			get_area = current->mm->get_unmapped_area;

  #endif

  		if (get_area)
  			rv = get_area(file, orig_addr, len, pgoff, flags);

  		else
  			rv = orig_addr;

  		unuse_pde(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 = kzalloc(sizeof(struct pde_opener), GFP_KERNEL);

  	if (!pdeo)
  		return -ENOMEM;

  	if (!use_pde(pde)) {

  		kfree(pdeo);

  		return -ENOENT;

  	}

  	open = pde->proc_fops->open;

  	release = pde->proc_fops->release;

  
  	if (open)
  		rv = open(inode, file);

  	if (rv == 0 && release) {
  		/* To know what to release. */

  		pdeo->file = file;
  		/* Strictly for "too late" ->release in proc_reg_release(). */

  		spin_lock(&pde->pde_unload_lock);

  		list_add(&pdeo->lh, &pde->pde_openers);

  		spin_unlock(&pde->pde_unload_lock);

  	} else
  		kfree(pdeo);

  
  	unuse_pde(pde);

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

  	struct pde_opener *pdeo;

  	spin_lock(&pde->pde_unload_lock);

  	list_for_each_entry(pdeo, &pde->pde_openers, lh) {
  		if (pdeo->file == file) {
  			close_pdeo(pde, pdeo);
  			break;
  		}

  	}

  	spin_unlock(&pde->pde_unload_lock);

  	return 0;

  }
  
  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,

  	.get_unmapped_area = proc_reg_get_unmapped_area,

  	.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,

  	.get_unmapped_area = proc_reg_get_unmapped_area,

  	.open		= proc_reg_open,
  	.release	= proc_reg_release,
  };
  #endif

  static void proc_put_link(void *p)
  {
  	unuse_pde(p);
  }

  static const char *proc_get_link(struct dentry *dentry,

  				 struct inode *inode,
  				 struct delayed_call *done)

  {

  	struct proc_dir_entry *pde = PDE(inode);

  	if (unlikely(!use_pde(pde)))
  		return ERR_PTR(-EINVAL);

  	set_delayed_call(done, proc_put_link, pde);

  	return pde->data;

  }

  const struct inode_operations proc_link_inode_operations = {
  	.readlink	= generic_readlink,

  	.get_link	= proc_get_link,

  };

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

  {

  	struct inode *inode = new_inode_pseudo(sb);

  	if (inode) {
  		inode->i_ino = de->low_ino;

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

  		PROC_I(inode)->pde = de;

  		if (is_empty_pde(de)) {
  			make_empty_dir_inode(inode);
  			return inode;
  		}

  		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);

  		WARN_ON(!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;

  			}

  		}

  	} else

  	       pde_put(de);

  	return inode;

  }

  int proc_fill_super(struct super_block *s)

  {

  	struct inode *root_inode;

  	int ret;

  	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) {

  		pr_err("proc_fill_super: get root inode failed
  ");

  		return -ENOMEM;
  	}

  	s->s_root = d_make_root(root_inode);
  	if (!s->s_root) {

  		pr_err("proc_fill_super: allocate dentry failed
  ");

  		return -ENOMEM;
  	}

  	ret = proc_setup_self(s);
  	if (ret) {
  		return ret;
  	}
  	return proc_setup_thread_self(s);

  }