fs/proc/proc_sysctl.c - kernel/mindspeed - Git at Google

 /*
  * /proc/sys support
  */
 #include <linux/init.h>
 #include <linux/sysctl.h>
 #include <linux/poll.h>
 #include <linux/proc_fs.h>
 #include <linux/security.h>
 #include <linux/namei.h>
 #include "internal.h"

 static const struct dentry_operations proc_sys_dentry_operations;
 static const struct file_operations proc_sys_file_operations;
 static const struct inode_operations proc_sys_inode_operations;
 static const struct file_operations proc_sys_dir_file_operations;
 static const struct inode_operations proc_sys_dir_operations;

 void proc_sys_poll_notify(struct ctl_table_poll *poll)
 {
 	if (!poll)
 		return;

 	atomic_inc(&poll->event);
 	wake_up_interruptible(&poll->wait);
 }

 static struct inode *proc_sys_make_inode(struct super_block *sb,
 		struct ctl_table_header *head, struct ctl_table *table)
 {
 	struct inode *inode;
 	struct proc_inode *ei;

 	inode = new_inode(sb);
 	if (!inode)
 		goto out;

 	inode->i_ino = get_next_ino();

 	sysctl_head_get(head);
 	ei = PROC_I(inode);
 	ei->sysctl = head;
 	ei->sysctl_entry = table;

 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 	inode->i_mode = table->mode;
 	if (!table->child) {
 		inode->i_mode |= S_IFREG;
 		inode->i_op = &proc_sys_inode_operations;
 		inode->i_fop = &proc_sys_file_operations;
 	} else {
 		inode->i_mode |= S_IFDIR;
 		clear_nlink(inode);
 		inode->i_op = &proc_sys_dir_operations;
 		inode->i_fop = &proc_sys_dir_file_operations;
 	}
 out:
 	return inode;
 }

 static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)
 {
 	int len;
 	for ( ; p->procname; p++) {

 		if (!p->procname)
 			continue;

 		len = strlen(p->procname);
 		if (len != name->len)
 			continue;

 		if (memcmp(p->procname, name->name, len) != 0)
 			continue;

 		/* I have a match */
 		return p;
 	}
 	return NULL;
 }

 static struct ctl_table_header *grab_header(struct inode *inode)
 {
 	if (PROC_I(inode)->sysctl)
 		return sysctl_head_grab(PROC_I(inode)->sysctl);
 	else
 		return sysctl_head_next(NULL);
 }

 static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
 					struct nameidata *nd)
 {
 	struct ctl_table_header *head = grab_header(dir);
 	struct ctl_table *table = PROC_I(dir)->sysctl_entry;
 	struct ctl_table_header *h = NULL;
 	struct qstr *name = &dentry->d_name;
 	struct ctl_table *p;
 	struct inode *inode;
 	struct dentry *err = ERR_PTR(-ENOENT);

 	if (IS_ERR(head))
 		return ERR_CAST(head);

 	if (table && !table->child) {
 		WARN_ON(1);
 		goto out;
 	}

 	table = table ? table->child : head->ctl_table;

 	p = find_in_table(table, name);
 	if (!p) {
 		for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
 			if (h->attached_to != table)
 				continue;
 			p = find_in_table(h->attached_by, name);
 			if (p)
 				break;
 		}
 	}

 	if (!p)
 		goto out;

 	err = ERR_PTR(-ENOMEM);
 	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
 	if (h)
 		sysctl_head_finish(h);

 	if (!inode)
 		goto out;

 	err = NULL;
 	d_set_d_op(dentry, &proc_sys_dentry_operations);
 	d_add(dentry, inode);

 out:
 	sysctl_head_finish(head);
 	return err;
 }

 static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
 		size_t count, loff_t *ppos, int write)
 {
 	struct inode *inode = filp->f_path.dentry->d_inode;
 	struct ctl_table_header *head = grab_header(inode);
 	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 	ssize_t error;
 	size_t res;

 	if (IS_ERR(head))
 		return PTR_ERR(head);

 	/*
 	 * At this point we know that the sysctl was not unregistered
 	 * and won't be until we finish.
 	 */
 	error = -EPERM;
 	if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))
 		goto out;

 	/* if that can happen at all, it should be -EINVAL, not -EISDIR */
 	error = -EINVAL;
 	if (!table->proc_handler)
 		goto out;

 	/* careful: calling conventions are nasty here */
 	res = count;
 	error = table->proc_handler(table, write, buf, &res, ppos);
 	if (!error)
 		error = res;
 out:
 	sysctl_head_finish(head);

 	return error;
 }

 static ssize_t proc_sys_read(struct file *filp, char __user *buf,
 				size_t count, loff_t *ppos)
 {
 	return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
 }

 static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
 				size_t count, loff_t *ppos)
 {
 	return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
 }

 static int proc_sys_open(struct inode *inode, struct file *filp)
 {
 	struct ctl_table_header *head = grab_header(inode);
 	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

 	/* sysctl was unregistered */
 	if (IS_ERR(head))
 		return PTR_ERR(head);

 	if (table->poll)
 		filp->private_data = proc_sys_poll_event(table->poll);

 	sysctl_head_finish(head);

 	return 0;
 }

 static unsigned int proc_sys_poll(struct file *filp, poll_table *wait)
 {
 	struct inode *inode = filp->f_path.dentry->d_inode;
 	struct ctl_table_header *head = grab_header(inode);
 	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 	unsigned int ret = DEFAULT_POLLMASK;
 	unsigned long event;

 	/* sysctl was unregistered */
 	if (IS_ERR(head))
 		return POLLERR | POLLHUP;

 	if (!table->proc_handler)
 		goto out;

 	if (!table->poll)
 		goto out;

 	event = (unsigned long)filp->private_data;
 	poll_wait(filp, &table->poll->wait, wait);

 	if (event != atomic_read(&table->poll->event)) {
 		filp->private_data = proc_sys_poll_event(table->poll);
 		ret = POLLIN | POLLRDNORM | POLLERR | POLLPRI;
 	}

 out:
 	sysctl_head_finish(head);

 	return ret;
 }

 static int proc_sys_fill_cache(struct file *filp, void *dirent,
 				filldir_t filldir,
 				struct ctl_table_header *head,
 				struct ctl_table *table)
 {
 	struct dentry *child, *dir = filp->f_path.dentry;
 	struct inode *inode;
 	struct qstr qname;
 	ino_t ino = 0;
 	unsigned type = DT_UNKNOWN;

 	qname.name = table->procname;
 	qname.len  = strlen(table->procname);
 	qname.hash = full_name_hash(qname.name, qname.len);

 	child = d_lookup(dir, &qname);
 	if (!child) {
 		child = d_alloc(dir, &qname);
 		if (child) {
 			inode = proc_sys_make_inode(dir->d_sb, head, table);
 			if (!inode) {
 				dput(child);
 				return -ENOMEM;
 			} else {
 				d_set_d_op(child, &proc_sys_dentry_operations);
 				d_add(child, inode);
 			}
 		} else {
 			return -ENOMEM;
 		}
 	}
 	inode = child->d_inode;
 	ino  = inode->i_ino;
 	type = inode->i_mode >> 12;
 	dput(child);
 	return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
 }

 static int scan(struct ctl_table_header *head, ctl_table *table,
 		unsigned long *pos, struct file *file,
 		void *dirent, filldir_t filldir)
 {

 	for (; table->procname; table++, (*pos)++) {
 		int res;

 		/* Can't do anything without a proc name */
 		if (!table->procname)
 			continue;

 		if (*pos < file->f_pos)
 			continue;

 		res = proc_sys_fill_cache(file, dirent, filldir, head, table);
 		if (res)
 			return res;

 		file->f_pos = *pos + 1;
 	}
 	return 0;
 }

 static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
 	struct dentry *dentry = filp->f_path.dentry;
 	struct inode *inode = dentry->d_inode;
 	struct ctl_table_header *head = grab_header(inode);
 	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 	struct ctl_table_header *h = NULL;
 	unsigned long pos;
 	int ret = -EINVAL;

 	if (IS_ERR(head))
 		return PTR_ERR(head);

 	if (table && !table->child) {
 		WARN_ON(1);
 		goto out;
 	}

 	table = table ? table->child : head->ctl_table;

 	ret = 0;
 	/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
 	if (filp->f_pos == 0) {
 		if (filldir(dirent, ".", 1, filp->f_pos,
 				inode->i_ino, DT_DIR) < 0)
 			goto out;
 		filp->f_pos++;
 	}
 	if (filp->f_pos == 1) {
 		if (filldir(dirent, "..", 2, filp->f_pos,
 				parent_ino(dentry), DT_DIR) < 0)
 			goto out;
 		filp->f_pos++;
 	}
 	pos = 2;

 	ret = scan(head, table, &pos, filp, dirent, filldir);
 	if (ret)
 		goto out;

 	for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
 		if (h->attached_to != table)
 			continue;
 		ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);
 		if (ret) {
 			sysctl_head_finish(h);
 			break;
 		}
 	}
 	ret = 1;
 out:
 	sysctl_head_finish(head);
 	return ret;
 }

 static int proc_sys_permission(struct inode *inode, int mask)
 {
 	/*
 	 * sysctl entries that are not writeable,
 	 * are _NOT_ writeable, capabilities or not.
 	 */
 	struct ctl_table_header *head;
 	struct ctl_table *table;
 	int error;

 	/* Executable files are not allowed under /proc/sys/ */
 	if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
 		return -EACCES;

 	head = grab_header(inode);
 	if (IS_ERR(head))
 		return PTR_ERR(head);

 	table = PROC_I(inode)->sysctl_entry;
 	if (!table) /* global root - r-xr-xr-x */
 		error = mask & MAY_WRITE ? -EACCES : 0;
 	else /* Use the permissions on the sysctl table entry */
 		error = sysctl_perm(head->root, table, mask & ~MAY_NOT_BLOCK);

 	sysctl_head_finish(head);
 	return error;
 }

 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
 {
 	struct inode *inode = dentry->d_inode;
 	int error;

 	if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
 		return -EPERM;

 	error = inode_change_ok(inode, attr);
 	if (error)
 		return error;

 	if ((attr->ia_valid & ATTR_SIZE) &&
 	    attr->ia_size != i_size_read(inode)) {
 		error = vmtruncate(inode, attr->ia_size);
 		if (error)
 			return error;
 	}

 	setattr_copy(inode, attr);
 	mark_inode_dirty(inode);
 	return 0;
 }

 static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 {
 	struct inode *inode = dentry->d_inode;
 	struct ctl_table_header *head = grab_header(inode);
 	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

 	if (IS_ERR(head))
 		return PTR_ERR(head);

 	generic_fillattr(inode, stat);
 	if (table)
 		stat->mode = (stat->mode & S_IFMT) | table->mode;

 	sysctl_head_finish(head);
 	return 0;
 }

 static const struct file_operations proc_sys_file_operations = {
 	.open		= proc_sys_open,
 	.poll		= proc_sys_poll,
 	.read		= proc_sys_read,
 	.write		= proc_sys_write,
 	.llseek		= default_llseek,
 };

 static const struct file_operations proc_sys_dir_file_operations = {
 	.read		= generic_read_dir,
 	.readdir	= proc_sys_readdir,
 	.llseek		= generic_file_llseek,
 };

 static const struct inode_operations proc_sys_inode_operations = {
 	.permission	= proc_sys_permission,
 	.setattr	= proc_sys_setattr,
 	.getattr	= proc_sys_getattr,
 };

 static const struct inode_operations proc_sys_dir_operations = {
 	.lookup		= proc_sys_lookup,
 	.permission	= proc_sys_permission,
 	.setattr	= proc_sys_setattr,
 	.getattr	= proc_sys_getattr,
 };

 static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
 	if (nd->flags & LOOKUP_RCU)
 		return -ECHILD;
 	return !PROC_I(dentry->d_inode)->sysctl->unregistering;
 }

 static int proc_sys_delete(const struct dentry *dentry)
 {
 	return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
 }

 static int proc_sys_compare(const struct dentry *parent,
 		const struct inode *pinode,
 		const struct dentry *dentry, const struct inode *inode,
 		unsigned int len, const char *str, const struct qstr *name)
 {
 	struct ctl_table_header *head;
 	/* Although proc doesn't have negative dentries, rcu-walk means
 	 * that inode here can be NULL */
 	/* AV: can it, indeed? */
 	if (!inode)
 		return 1;
 	if (name->len != len)
 		return 1;
 	if (memcmp(name->name, str, len))
 		return 1;
 	head = rcu_dereference(PROC_I(inode)->sysctl);
 	return !head || !sysctl_is_seen(head);
 }

 static const struct dentry_operations proc_sys_dentry_operations = {
 	.d_revalidate	= proc_sys_revalidate,
 	.d_delete	= proc_sys_delete,
 	.d_compare	= proc_sys_compare,
 };

 int __init proc_sys_init(void)
 {
 	struct proc_dir_entry *proc_sys_root;

 	proc_sys_root = proc_mkdir("sys", NULL);
 	proc_sys_root->proc_iops = &proc_sys_dir_operations;
 	proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
 	proc_sys_root->nlink = 0;
 	return 0;
 }
	/*
	* /proc/sys support
	*/
	#include <linux/init.h>
	#include <linux/sysctl.h>
	#include <linux/poll.h>
	#include <linux/proc_fs.h>
	#include <linux/security.h>
	#include <linux/namei.h>
	#include "internal.h"

	static const struct dentry_operations proc_sys_dentry_operations;
	static const struct file_operations proc_sys_file_operations;
	static const struct inode_operations proc_sys_inode_operations;
	static const struct file_operations proc_sys_dir_file_operations;
	static const struct inode_operations proc_sys_dir_operations;

	void proc_sys_poll_notify(struct ctl_table_poll *poll)
	{
	if (!poll)
	return;

	atomic_inc(&poll->event);
	wake_up_interruptible(&poll->wait);
	}

	static struct inode proc_sys_make_inode(struct super_block sb,
	struct ctl_table_header head, struct ctl_table table)
	{
	struct inode *inode;
	struct proc_inode *ei;

	inode = new_inode(sb);
	if (!inode)
	goto out;

	inode->i_ino = get_next_ino();

	sysctl_head_get(head);
	ei = PROC_I(inode);
	ei->sysctl = head;
	ei->sysctl_entry = table;

	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->i_mode = table->mode;
	if (!table->child) {
	inode->i_mode \|= S_IFREG;
	inode->i_op = &proc_sys_inode_operations;
	inode->i_fop = &proc_sys_file_operations;
	} else {
	inode->i_mode \|= S_IFDIR;
	clear_nlink(inode);
	inode->i_op = &proc_sys_dir_operations;
	inode->i_fop = &proc_sys_dir_file_operations;
	}
	out:
	return inode;
	}

	static struct ctl_table find_in_table(struct ctl_table p, struct qstr *name)
	{
	int len;
	for ( ; p->procname; p++) {

	if (!p->procname)
	continue;

	len = strlen(p->procname);
	if (len != name->len)
	continue;

	if (memcmp(p->procname, name->name, len) != 0)
	continue;

	/* I have a match */
	return p;
	}
	return NULL;
	}

	static struct ctl_table_header grab_header(struct inode inode)
	{
	if (PROC_I(inode)->sysctl)
	return sysctl_head_grab(PROC_I(inode)->sysctl);
	else
	return sysctl_head_next(NULL);
	}

	static struct dentry proc_sys_lookup(struct inode dir, struct dentry *dentry,
	struct nameidata *nd)
	{
	struct ctl_table_header *head = grab_header(dir);
	struct ctl_table *table = PROC_I(dir)->sysctl_entry;
	struct ctl_table_header *h = NULL;
	struct qstr *name = &dentry->d_name;
	struct ctl_table *p;
	struct inode *inode;
	struct dentry *err = ERR_PTR(-ENOENT);

	if (IS_ERR(head))
	return ERR_CAST(head);

	if (table && !table->child) {
	WARN_ON(1);
	goto out;
	}

	table = table ? table->child : head->ctl_table;

	p = find_in_table(table, name);
	if (!p) {
	for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
	if (h->attached_to != table)
	continue;
	p = find_in_table(h->attached_by, name);
	if (p)
	break;
	}
	}

	if (!p)
	goto out;

	err = ERR_PTR(-ENOMEM);
	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
	if (h)
	sysctl_head_finish(h);

	if (!inode)
	goto out;

	err = NULL;
	d_set_d_op(dentry, &proc_sys_dentry_operations);
	d_add(dentry, inode);

	out:
	sysctl_head_finish(head);
	return err;
	}

	static ssize_t proc_sys_call_handler(struct file filp, void __user buf,
	size_t count, loff_t *ppos, int write)
	{
	struct inode *inode = filp->f_path.dentry->d_inode;
	struct ctl_table_header *head = grab_header(inode);
	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
	ssize_t error;
	size_t res;

	if (IS_ERR(head))
	return PTR_ERR(head);

	/*
	* At this point we know that the sysctl was not unregistered
	* and won't be until we finish.
	*/
	error = -EPERM;
	if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))
	goto out;

	/* if that can happen at all, it should be -EINVAL, not -EISDIR */
	error = -EINVAL;
	if (!table->proc_handler)
	goto out;

	/* careful: calling conventions are nasty here */
	res = count;
	error = table->proc_handler(table, write, buf, &res, ppos);
	if (!error)
	error = res;
	out:
	sysctl_head_finish(head);

	return error;
	}

	static ssize_t proc_sys_read(struct file filp, char __user buf,
	size_t count, loff_t *ppos)
	{
	return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
	}

	static ssize_t proc_sys_write(struct file filp, const char __user buf,
	size_t count, loff_t *ppos)
	{
	return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
	}

	static int proc_sys_open(struct inode inode, struct file filp)
	{
	struct ctl_table_header *head = grab_header(inode);
	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

	/* sysctl was unregistered */
	if (IS_ERR(head))
	return PTR_ERR(head);

	if (table->poll)
	filp->private_data = proc_sys_poll_event(table->poll);

	sysctl_head_finish(head);

	return 0;
	}

	static unsigned int proc_sys_poll(struct file filp, poll_table wait)
	{
	struct inode *inode = filp->f_path.dentry->d_inode;
	struct ctl_table_header *head = grab_header(inode);
	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
	unsigned int ret = DEFAULT_POLLMASK;
	unsigned long event;

	/* sysctl was unregistered */
	if (IS_ERR(head))
	return POLLERR \| POLLHUP;

	if (!table->proc_handler)
	goto out;

	if (!table->poll)
	goto out;

	event = (unsigned long)filp->private_data;
	poll_wait(filp, &table->poll->wait, wait);

	if (event != atomic_read(&table->poll->event)) {
	filp->private_data = proc_sys_poll_event(table->poll);
	ret = POLLIN \| POLLRDNORM \| POLLERR \| POLLPRI;
	}

	out:
	sysctl_head_finish(head);

	return ret;
	}

	static int proc_sys_fill_cache(struct file filp, void dirent,
	filldir_t filldir,
	struct ctl_table_header *head,
	struct ctl_table *table)
	{
	struct dentry child, dir = filp->f_path.dentry;
	struct inode *inode;
	struct qstr qname;
	ino_t ino = 0;
	unsigned type = DT_UNKNOWN;

	qname.name = table->procname;
	qname.len = strlen(table->procname);
	qname.hash = full_name_hash(qname.name, qname.len);

	child = d_lookup(dir, &qname);
	if (!child) {
	child = d_alloc(dir, &qname);
	if (child) {
	inode = proc_sys_make_inode(dir->d_sb, head, table);
	if (!inode) {
	dput(child);
	return -ENOMEM;
	} else {
	d_set_d_op(child, &proc_sys_dentry_operations);
	d_add(child, inode);
	}
	} else {
	return -ENOMEM;
	}
	}
	inode = child->d_inode;
	ino = inode->i_ino;
	type = inode->i_mode >> 12;
	dput(child);
	return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
	}

	static int scan(struct ctl_table_header head, ctl_table table,
	unsigned long pos, struct file file,
	void *dirent, filldir_t filldir)
	{

	for (; table->procname; table++, (*pos)++) {
	int res;

	/* Can't do anything without a proc name */
	if (!table->procname)
	continue;

	if (*pos < file->f_pos)
	continue;

	res = proc_sys_fill_cache(file, dirent, filldir, head, table);
	if (res)
	return res;

	file->f_pos = *pos + 1;
	}
	return 0;
	}

	static int proc_sys_readdir(struct file filp, void dirent, filldir_t filldir)
	{
	struct dentry *dentry = filp->f_path.dentry;
	struct inode *inode = dentry->d_inode;
	struct ctl_table_header *head = grab_header(inode);
	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
	struct ctl_table_header *h = NULL;
	unsigned long pos;
	int ret = -EINVAL;

	if (IS_ERR(head))
	return PTR_ERR(head);

	if (table && !table->child) {
	WARN_ON(1);
	goto out;
	}

	table = table ? table->child : head->ctl_table;

	ret = 0;
	/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
	if (filp->f_pos == 0) {
	if (filldir(dirent, ".", 1, filp->f_pos,
	inode->i_ino, DT_DIR) < 0)
	goto out;
	filp->f_pos++;
	}
	if (filp->f_pos == 1) {
	if (filldir(dirent, "..", 2, filp->f_pos,
	parent_ino(dentry), DT_DIR) < 0)
	goto out;
	filp->f_pos++;
	}
	pos = 2;

	ret = scan(head, table, &pos, filp, dirent, filldir);
	if (ret)
	goto out;

	for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
	if (h->attached_to != table)
	continue;
	ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);
	if (ret) {
	sysctl_head_finish(h);
	break;
	}
	}
	ret = 1;
	out:
	sysctl_head_finish(head);
	return ret;
	}

	static int proc_sys_permission(struct inode *inode, int mask)
	{
	/*
	* sysctl entries that are not writeable,
	* are _NOT_ writeable, capabilities or not.
	*/
	struct ctl_table_header *head;
	struct ctl_table *table;
	int error;

	/* Executable files are not allowed under /proc/sys/ */
	if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
	return -EACCES;

	head = grab_header(inode);
	if (IS_ERR(head))
	return PTR_ERR(head);

	table = PROC_I(inode)->sysctl_entry;
	if (!table) /* global root - r-xr-xr-x */
	error = mask & MAY_WRITE ? -EACCES : 0;
	else /* Use the permissions on the sysctl table entry */
	error = sysctl_perm(head->root, table, mask & ~MAY_NOT_BLOCK);

	sysctl_head_finish(head);
	return error;
	}

	static int proc_sys_setattr(struct dentry dentry, struct iattr attr)
	{
	struct inode *inode = dentry->d_inode;
	int error;

	if (attr->ia_valid & (ATTR_MODE \| ATTR_UID \| ATTR_GID))
	return -EPERM;

	error = inode_change_ok(inode, attr);
	if (error)
	return error;

	if ((attr->ia_valid & ATTR_SIZE) &&
	attr->ia_size != i_size_read(inode)) {
	error = vmtruncate(inode, attr->ia_size);
	if (error)
	return error;
	}

	setattr_copy(inode, attr);
	mark_inode_dirty(inode);
	return 0;
	}

	static int proc_sys_getattr(struct vfsmount mnt, struct dentry dentry, struct kstat *stat)
	{
	struct inode *inode = dentry->d_inode;
	struct ctl_table_header *head = grab_header(inode);
	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

	if (IS_ERR(head))
	return PTR_ERR(head);

	generic_fillattr(inode, stat);
	if (table)
	stat->mode = (stat->mode & S_IFMT) \| table->mode;

	sysctl_head_finish(head);
	return 0;
	}

	static const struct file_operations proc_sys_file_operations = {
	.open = proc_sys_open,
	.poll = proc_sys_poll,
	.read = proc_sys_read,
	.write = proc_sys_write,
	.llseek = default_llseek,
	};

	static const struct file_operations proc_sys_dir_file_operations = {
	.read = generic_read_dir,
	.readdir = proc_sys_readdir,
	.llseek = generic_file_llseek,
	};

	static const struct inode_operations proc_sys_inode_operations = {
	.permission = proc_sys_permission,
	.setattr = proc_sys_setattr,
	.getattr = proc_sys_getattr,
	};

	static const struct inode_operations proc_sys_dir_operations = {
	.lookup = proc_sys_lookup,
	.permission = proc_sys_permission,
	.setattr = proc_sys_setattr,
	.getattr = proc_sys_getattr,
	};

	static int proc_sys_revalidate(struct dentry dentry, struct nameidata nd)
	{
	if (nd->flags & LOOKUP_RCU)
	return -ECHILD;
	return !PROC_I(dentry->d_inode)->sysctl->unregistering;
	}

	static int proc_sys_delete(const struct dentry *dentry)
	{
	return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
	}

	static int proc_sys_compare(const struct dentry *parent,
	const struct inode *pinode,
	const struct dentry dentry, const struct inode inode,
	unsigned int len, const char str, const struct qstr name)
	{
	struct ctl_table_header *head;
	/* Although proc doesn't have negative dentries, rcu-walk means
	* that inode here can be NULL */
	/* AV: can it, indeed? */
	if (!inode)
	return 1;
	if (name->len != len)
	return 1;
	if (memcmp(name->name, str, len))
	return 1;
	head = rcu_dereference(PROC_I(inode)->sysctl);
	return !head \|\| !sysctl_is_seen(head);
	}

	static const struct dentry_operations proc_sys_dentry_operations = {
	.d_revalidate = proc_sys_revalidate,
	.d_delete = proc_sys_delete,
	.d_compare = proc_sys_compare,
	};

	int __init proc_sys_init(void)
	{
	struct proc_dir_entry *proc_sys_root;

	proc_sys_root = proc_mkdir("sys", NULL);
	proc_sys_root->proc_iops = &proc_sys_dir_operations;
	proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
	proc_sys_root->nlink = 0;
	return 0;
	}