fs/proc/inode.c - kernel/lockdown - Git at Google

 /*
  *  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 <linux/namei.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_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_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	struct proc_dir_entry *pde = PDE(d_inode(dentry));
 	if (unlikely(!use_pde(pde)))
 		return ERR_PTR(-EINVAL);
 	nd_set_link(nd, pde->data);
 	return pde;
 }

 static void proc_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
 {
 	unuse_pde(p);
 }

 const struct inode_operations proc_link_inode_operations = {
 	.readlink	= generic_readlink,
 	.follow_link	= proc_follow_link,
 	.put_link	= proc_put_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\n");
 		return -ENOMEM;
 	}

 	s->s_root = d_make_root(root_inode);
 	if (!s->s_root) {
 		pr_err("proc_fill_super: allocate dentry failed\n");
 		return -ENOMEM;
 	}

 	ret = proc_setup_self(s);
 	if (ret) {
 		return ret;
 	}
 	return proc_setup_thread_self(s);
 }
	/*
	* 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 <linux/namei.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_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_follow_link(struct dentry dentry, struct nameidata *nd)
	{
	struct proc_dir_entry *pde = PDE(d_inode(dentry));
	if (unlikely(!use_pde(pde)))
	return ERR_PTR(-EINVAL);
	nd_set_link(nd, pde->data);
	return pde;
	}

	static void proc_put_link(struct dentry dentry, struct nameidata nd, void *p)
	{
	unuse_pde(p);
	}

	const struct inode_operations proc_link_inode_operations = {
	.readlink = generic_readlink,
	.follow_link = proc_follow_link,
	.put_link = proc_put_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\n");
	return -ENOMEM;
	}

	s->s_root = d_make_root(root_inode);
	if (!s->s_root) {
	pr_err("proc_fill_super: allocate dentry failed\n");
	return -ENOMEM;
	}

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