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41 results

raw.c

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  • Forked from hardware-enablement / Rockchip upstream enablement efforts / linux
    Source project has a limited visibility.
    generic.c 18.38 KiB
    // SPDX-License-Identifier: GPL-2.0-only
    /*
     * 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/cache.h>
    #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/namei.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 <linux/uaccess.h>
    #include <linux/seq_file.h>
    
    #include "internal.h"
    
    static DEFINE_RWLOCK(proc_subdir_lock);
    
    struct kmem_cache *proc_dir_entry_cache __ro_after_init;
    
    void pde_free(struct proc_dir_entry *pde)
    {
    	if (S_ISLNK(pde->mode))
    		kfree(pde->data);
    	if (pde->name != pde->inline_name)
    		kfree(pde->name);
    	kmem_cache_free(proc_dir_entry_cache, pde);
    }
    
    static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int len)
    {
    	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 = rb_entry(node,
    						     struct proc_dir_entry,
    						     subdir_node);
    		int result = proc_match(name, de, len);
    
    		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 = rb_entry(*new,
    						       struct proc_dir_entry,
    						       subdir_node);
    		int result = proc_match(de->name, this, de->namelen);
    
    		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 = setattr_prepare(dentry, 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(const struct path *path, struct kstat *stat,
    			u32 request_mask, unsigned int query_flags)
    {
    	struct inode *inode = d_inode(path->dentry);
    	struct proc_dir_entry *de = PDE(inode);
    	if (de) {
    		nlink_t nlink = READ_ONCE(de->nlink);
    		if (nlink > 0) {
    			set_nlink(inode, 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;
    
    	de = *ret;
    	if (!de)
    		de = &proc_root;
    
    	while (1) {
    		next = strchr(cp, '/');
    		if (!next)
    			break;
    
    		de = pde_subdir_find(de, cp, next - cp);
    		if (!de) {
    			WARN(1, "name '%s'\n", name);
    			return -ENOENT;
    		}
    		cp = next + 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);
    
    #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)
    {
    	int i;
    
    	i = ida_simple_get(&proc_inum_ida, 0, UINT_MAX - PROC_DYNAMIC_FIRST + 1,
    			   GFP_KERNEL);
    	if (i < 0)
    		return i;
    
    	*inum = PROC_DYNAMIC_FIRST + (unsigned int)i;
    	return 0;
    }
    
    void proc_free_inum(unsigned int inum)
    {
    	ida_simple_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
    }
    
    static int proc_misc_d_revalidate(struct dentry *dentry, unsigned int flags)
    {
    	if (flags & LOOKUP_RCU)
    		return -ECHILD;
    
    	if (atomic_read(&PDE(d_inode(dentry))->in_use) < 0)
    		return 0; /* revalidate */
    	return 1;
    }
    
    static int proc_misc_d_delete(const struct dentry *dentry)
    {
    	return atomic_read(&PDE(d_inode(dentry))->in_use) < 0;
    }
    
    static const struct dentry_operations proc_misc_dentry_ops = {
    	.d_revalidate	= proc_misc_d_revalidate,
    	.d_delete	= proc_misc_d_delete,
    };
    
    /*
     * Don't create negative dentries here, return -ENOENT by hand
     * instead.
     */
    struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
    			      struct proc_dir_entry *de)
    {
    	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, de->proc_dops);
    		return d_splice_alias(inode, dentry);
    	}
    	read_unlock(&proc_subdir_lock);
    	return ERR_PTR(-ENOENT);
    }
    
    struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
    		unsigned int flags)
    {
    	struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb);
    
    	if (fs_info->pidonly == PROC_PIDONLY_ON)
    		return ERR_PTR(-ENOENT);
    
    	return proc_lookup_de(dir, dentry, PDE(dir));
    }
    
    /*
     * 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 file *file, struct dir_context *ctx,
    		    struct proc_dir_entry *de)
    {
    	int i;
    
    	if (!dir_emit_dots(file, ctx))
    		return 0;
    
    	i = ctx->pos - 2;
    	read_lock(&proc_subdir_lock);
    	de = pde_subdir_first(de);
    	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;
    		}
    		ctx->pos++;
    		read_lock(&proc_subdir_lock);
    		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);
    	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
    
    	if (fs_info->pidonly == PROC_PIDONLY_ON)
    		return 1;
    
    	return proc_readdir_de(file, ctx, PDE(inode));
    }
    
    /*
     * 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_shared		= 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,
    };
    
    /* returns the registered entry, or frees dp and returns NULL on failure */
    struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
    		struct proc_dir_entry *dp)
    {
    	if (proc_alloc_inum(&dp->low_ino))
    		goto out_free_entry;
    
    	write_lock(&proc_subdir_lock);
    	dp->parent = dir;
    	if (pde_subdir_insert(dir, dp) == false) {
    		WARN(1, "proc_dir_entry '%s/%s' already registered\n",
    		     dir->name, dp->name);
    		write_unlock(&proc_subdir_lock);
    		goto out_free_inum;
    	}
    	dir->nlink++;
    	write_unlock(&proc_subdir_lock);
    
    	return dp;
    out_free_inum:
    	proc_free_inum(dp->low_ino);
    out_free_entry:
    	pde_free(dp);
    	return NULL;
    }
    
    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\n", qstr.len);
    		return NULL;
    	}
    	if (qstr.len == 1 && fn[0] == '.') {
    		WARN(1, "name '.'\n");
    		return NULL;
    	}
    	if (qstr.len == 2 && fn[0] == '.' && fn[1] == '.') {
    		WARN(1, "name '..'\n");
    		return NULL;
    	}
    	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
    		WARN(1, "create '/proc/%s' by hand\n", qstr.name);
    		return NULL;
    	}
    	if (is_empty_pde(*parent)) {
    		WARN(1, "attempt to add to permanently empty directory");
    		return NULL;
    	}
    
    	ent = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);
    	if (!ent)
    		goto out;
    
    	if (qstr.len + 1 <= SIZEOF_PDE_INLINE_NAME) {
    		ent->name = ent->inline_name;
    	} else {
    		ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);
    		if (!ent->name) {
    			pde_free(ent);
    			return NULL;
    		}
    	}
    
    	memcpy(ent->name, fn, qstr.len + 1);
    	ent->namelen = qstr.len;
    	ent->mode = mode;
    	ent->nlink = nlink;
    	ent->subdir = RB_ROOT;
    	refcount_set(&ent->refcnt, 1);
    	spin_lock_init(&ent->pde_unload_lock);
    	INIT_LIST_HEAD(&ent->pde_openers);
    	proc_set_user(ent, (*parent)->uid, (*parent)->gid);
    
    	ent->proc_dops = &proc_misc_dentry_ops;
    
    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;
    			ent = proc_register(parent, ent);
    		} else {
    			pde_free(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_dir_ops = &proc_dir_operations;
    		ent->proc_iops = &proc_dir_inode_operations;
    		ent = proc_register(parent, ent);
    	}
    	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_dir_ops = NULL;
    		ent->proc_iops = NULL;
    		ent = proc_register(parent, ent);
    	}
    	return ent;
    }
    EXPORT_SYMBOL(proc_create_mount_point);
    
    struct proc_dir_entry *proc_create_reg(const char *name, umode_t mode,
    		struct proc_dir_entry **parent, void *data)
    {
    	struct proc_dir_entry *p;
    
    	if ((mode & S_IFMT) == 0)
    		mode |= S_IFREG;
    	if ((mode & S_IALLUGO) == 0)
    		mode |= S_IRUGO;
    	if (WARN_ON_ONCE(!S_ISREG(mode)))
    		return NULL;
    
    	p = __proc_create(parent, name, mode, 1);
    	if (p) {
    		p->proc_iops = &proc_file_inode_operations;
    		p->data = data;
    	}
    	return p;
    }
    
    static inline void pde_set_flags(struct proc_dir_entry *pde)
    {
    	if (pde->proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
    		pde->flags |= PROC_ENTRY_PERMANENT;
    }
    
    struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
    		struct proc_dir_entry *parent,
    		const struct proc_ops *proc_ops, void *data)
    {
    	struct proc_dir_entry *p;
    
    	p = proc_create_reg(name, mode, &parent, data);
    	if (!p)
    		return NULL;
    	p->proc_ops = proc_ops;
    	pde_set_flags(p);
    	return proc_register(parent, p);
    }
    EXPORT_SYMBOL(proc_create_data);
     
    struct proc_dir_entry *proc_create(const char *name, umode_t mode,
    				   struct proc_dir_entry *parent,
    				   const struct proc_ops *proc_ops)
    {
    	return proc_create_data(name, mode, parent, proc_ops, NULL);
    }
    EXPORT_SYMBOL(proc_create);
    
    static int proc_seq_open(struct inode *inode, struct file *file)
    {
    	struct proc_dir_entry *de = PDE(inode);
    
    	if (de->state_size)
    		return seq_open_private(file, de->seq_ops, de->state_size);
    	return seq_open(file, de->seq_ops);
    }
    
    static int proc_seq_release(struct inode *inode, struct file *file)
    {
    	struct proc_dir_entry *de = PDE(inode);
    
    	if (de->state_size)
    		return seq_release_private(inode, file);
    	return seq_release(inode, file);
    }
    
    static const struct proc_ops proc_seq_ops = {
    	/* not permanent -- can call into arbitrary seq_operations */
    	.proc_open	= proc_seq_open,
    	.proc_read_iter	= seq_read_iter,
    	.proc_lseek	= seq_lseek,
    	.proc_release	= proc_seq_release,
    };
    
    struct proc_dir_entry *proc_create_seq_private(const char *name, umode_t mode,
    		struct proc_dir_entry *parent, const struct seq_operations *ops,
    		unsigned int state_size, void *data)
    {
    	struct proc_dir_entry *p;
    
    	p = proc_create_reg(name, mode, &parent, data);
    	if (!p)
    		return NULL;
    	p->proc_ops = &proc_seq_ops;
    	p->seq_ops = ops;
    	p->state_size = state_size;
    	return proc_register(parent, p);
    }
    EXPORT_SYMBOL(proc_create_seq_private);
    
    static int proc_single_open(struct inode *inode, struct file *file)
    {
    	struct proc_dir_entry *de = PDE(inode);
    
    	return single_open(file, de->single_show, de->data);
    }
    
    static const struct proc_ops proc_single_ops = {
    	/* not permanent -- can call into arbitrary ->single_show */
    	.proc_open	= proc_single_open,
    	.proc_read_iter = seq_read_iter,
    	.proc_lseek	= seq_lseek,
    	.proc_release	= single_release,
    };
    
    struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
    		struct proc_dir_entry *parent,
    		int (*show)(struct seq_file *, void *), void *data)
    {
    	struct proc_dir_entry *p;
    
    	p = proc_create_reg(name, mode, &parent, data);
    	if (!p)
    		return NULL;
    	p->proc_ops = &proc_single_ops;
    	p->single_show = show;
    	return proc_register(parent, p);
    }
    EXPORT_SYMBOL(proc_create_single_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);
    
    void pde_put(struct proc_dir_entry *pde)
    {
    	if (refcount_dec_and_test(&pde->refcnt)) {
    		proc_free_inum(pde->low_ino);
    		pde_free(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) {
    		if (unlikely(pde_is_permanent(de))) {
    			WARN(1, "removing permanent /proc entry '%s'", de->name);
    			de = NULL;
    		} else {
    			rb_erase(&de->subdir_node, &parent->subdir);
    			if (S_ISDIR(de->mode))
    				parent->nlink--;
    		}
    	}
    	write_unlock(&proc_subdir_lock);
    	if (!de) {
    		WARN(1, "name '%s'\n", name);
    		return;
    	}
    
    	proc_entry_rundown(de);
    
    	WARN(pde_subdir_first(de),
    	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",
    	     __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;
    	}
    	if (unlikely(pde_is_permanent(root))) {
    		write_unlock(&proc_subdir_lock);
    		WARN(1, "removing permanent /proc entry '%s/%s'",
    			root->parent->name, root->name);
    		return -EINVAL;
    	}
    	rb_erase(&root->subdir_node, &parent->subdir);
    
    	de = root;
    	while (1) {
    		next = pde_subdir_first(de);
    		if (next) {
    			if (unlikely(pde_is_permanent(root))) {
    				write_unlock(&proc_subdir_lock);
    				WARN(1, "removing permanent /proc entry '%s/%s'",
    					next->parent->name, next->name);
    				return -EINVAL;
    			}
    			rb_erase(&next->subdir_node, &de->subdir);
    			de = next;
    			continue;
    		}
    		next = de->parent;
    		if (S_ISDIR(de->mode))
    			next->nlink--;
    		write_unlock(&proc_subdir_lock);
    
    		proc_entry_rundown(de);
    		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);
    
    /*
     * Pull a user buffer into memory and pass it to the file's write handler if
     * one is supplied.  The ->write() method is permitted to modify the
     * kernel-side buffer.
     */
    ssize_t proc_simple_write(struct file *f, const char __user *ubuf, size_t size,
    			  loff_t *_pos)
    {
    	struct proc_dir_entry *pde = PDE(file_inode(f));
    	char *buf;
    	int ret;
    
    	if (!pde->write)
    		return -EACCES;
    	if (size == 0 || size > PAGE_SIZE - 1)
    		return -EINVAL;
    	buf = memdup_user_nul(ubuf, size);
    	if (IS_ERR(buf))
    		return PTR_ERR(buf);
    	ret = pde->write(f, buf, size);
    	kfree(buf);
    	return ret == 0 ? size : ret;
    }