xref: /openbmc/linux/fs/proc/generic.c (revision ae213c44) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * proc/fs/generic.c --- generic routines for the proc-fs
4  *
5  * This file contains generic proc-fs routines for handling
6  * directories and files.
7  *
8  * Copyright (C) 1991, 1992 Linus Torvalds.
9  * Copyright (C) 1997 Theodore Ts'o
10  */
11 
12 #include <linux/cache.h>
13 #include <linux/errno.h>
14 #include <linux/time.h>
15 #include <linux/proc_fs.h>
16 #include <linux/stat.h>
17 #include <linux/mm.h>
18 #include <linux/module.h>
19 #include <linux/namei.h>
20 #include <linux/slab.h>
21 #include <linux/printk.h>
22 #include <linux/mount.h>
23 #include <linux/init.h>
24 #include <linux/idr.h>
25 #include <linux/bitops.h>
26 #include <linux/spinlock.h>
27 #include <linux/completion.h>
28 #include <linux/uaccess.h>
29 #include <linux/seq_file.h>
30 
31 #include "internal.h"
32 
33 static DEFINE_RWLOCK(proc_subdir_lock);
34 
35 struct kmem_cache *proc_dir_entry_cache __ro_after_init;
36 
37 void pde_free(struct proc_dir_entry *pde)
38 {
39 	if (S_ISLNK(pde->mode))
40 		kfree(pde->data);
41 	if (pde->name != pde->inline_name)
42 		kfree(pde->name);
43 	kmem_cache_free(proc_dir_entry_cache, pde);
44 }
45 
46 static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int len)
47 {
48 	if (len < de->namelen)
49 		return -1;
50 	if (len > de->namelen)
51 		return 1;
52 
53 	return memcmp(name, de->name, len);
54 }
55 
56 static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)
57 {
58 	return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,
59 			     subdir_node);
60 }
61 
62 static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
63 {
64 	return rb_entry_safe(rb_next(&dir->subdir_node), struct proc_dir_entry,
65 			     subdir_node);
66 }
67 
68 static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,
69 					      const char *name,
70 					      unsigned int len)
71 {
72 	struct rb_node *node = dir->subdir.rb_node;
73 
74 	while (node) {
75 		struct proc_dir_entry *de = rb_entry(node,
76 						     struct proc_dir_entry,
77 						     subdir_node);
78 		int result = proc_match(name, de, len);
79 
80 		if (result < 0)
81 			node = node->rb_left;
82 		else if (result > 0)
83 			node = node->rb_right;
84 		else
85 			return de;
86 	}
87 	return NULL;
88 }
89 
90 static bool pde_subdir_insert(struct proc_dir_entry *dir,
91 			      struct proc_dir_entry *de)
92 {
93 	struct rb_root *root = &dir->subdir;
94 	struct rb_node **new = &root->rb_node, *parent = NULL;
95 
96 	/* Figure out where to put new node */
97 	while (*new) {
98 		struct proc_dir_entry *this = rb_entry(*new,
99 						       struct proc_dir_entry,
100 						       subdir_node);
101 		int result = proc_match(de->name, this, de->namelen);
102 
103 		parent = *new;
104 		if (result < 0)
105 			new = &(*new)->rb_left;
106 		else if (result > 0)
107 			new = &(*new)->rb_right;
108 		else
109 			return false;
110 	}
111 
112 	/* Add new node and rebalance tree. */
113 	rb_link_node(&de->subdir_node, parent, new);
114 	rb_insert_color(&de->subdir_node, root);
115 	return true;
116 }
117 
118 static int proc_notify_change(struct dentry *dentry, struct iattr *iattr)
119 {
120 	struct inode *inode = d_inode(dentry);
121 	struct proc_dir_entry *de = PDE(inode);
122 	int error;
123 
124 	error = setattr_prepare(dentry, iattr);
125 	if (error)
126 		return error;
127 
128 	setattr_copy(inode, iattr);
129 	mark_inode_dirty(inode);
130 
131 	proc_set_user(de, inode->i_uid, inode->i_gid);
132 	de->mode = inode->i_mode;
133 	return 0;
134 }
135 
136 static int proc_getattr(const struct path *path, struct kstat *stat,
137 			u32 request_mask, unsigned int query_flags)
138 {
139 	struct inode *inode = d_inode(path->dentry);
140 	struct proc_dir_entry *de = PDE(inode);
141 	if (de && de->nlink)
142 		set_nlink(inode, de->nlink);
143 
144 	generic_fillattr(inode, stat);
145 	return 0;
146 }
147 
148 static const struct inode_operations proc_file_inode_operations = {
149 	.setattr	= proc_notify_change,
150 };
151 
152 /*
153  * This function parses a name such as "tty/driver/serial", and
154  * returns the struct proc_dir_entry for "/proc/tty/driver", and
155  * returns "serial" in residual.
156  */
157 static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
158 			     const char **residual)
159 {
160 	const char     		*cp = name, *next;
161 	struct proc_dir_entry	*de;
162 	unsigned int		len;
163 
164 	de = *ret;
165 	if (!de)
166 		de = &proc_root;
167 
168 	while (1) {
169 		next = strchr(cp, '/');
170 		if (!next)
171 			break;
172 
173 		len = next - cp;
174 		de = pde_subdir_find(de, cp, len);
175 		if (!de) {
176 			WARN(1, "name '%s'\n", name);
177 			return -ENOENT;
178 		}
179 		cp += len + 1;
180 	}
181 	*residual = cp;
182 	*ret = de;
183 	return 0;
184 }
185 
186 static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
187 			   const char **residual)
188 {
189 	int rv;
190 
191 	read_lock(&proc_subdir_lock);
192 	rv = __xlate_proc_name(name, ret, residual);
193 	read_unlock(&proc_subdir_lock);
194 	return rv;
195 }
196 
197 static DEFINE_IDA(proc_inum_ida);
198 
199 #define PROC_DYNAMIC_FIRST 0xF0000000U
200 
201 /*
202  * Return an inode number between PROC_DYNAMIC_FIRST and
203  * 0xffffffff, or zero on failure.
204  */
205 int proc_alloc_inum(unsigned int *inum)
206 {
207 	int i;
208 
209 	i = ida_simple_get(&proc_inum_ida, 0, UINT_MAX - PROC_DYNAMIC_FIRST + 1,
210 			   GFP_KERNEL);
211 	if (i < 0)
212 		return i;
213 
214 	*inum = PROC_DYNAMIC_FIRST + (unsigned int)i;
215 	return 0;
216 }
217 
218 void proc_free_inum(unsigned int inum)
219 {
220 	ida_simple_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
221 }
222 
223 static int proc_misc_d_revalidate(struct dentry *dentry, unsigned int flags)
224 {
225 	if (flags & LOOKUP_RCU)
226 		return -ECHILD;
227 
228 	if (atomic_read(&PDE(d_inode(dentry))->in_use) < 0)
229 		return 0; /* revalidate */
230 	return 1;
231 }
232 
233 static int proc_misc_d_delete(const struct dentry *dentry)
234 {
235 	return atomic_read(&PDE(d_inode(dentry))->in_use) < 0;
236 }
237 
238 static const struct dentry_operations proc_misc_dentry_ops = {
239 	.d_revalidate	= proc_misc_d_revalidate,
240 	.d_delete	= proc_misc_d_delete,
241 };
242 
243 /*
244  * Don't create negative dentries here, return -ENOENT by hand
245  * instead.
246  */
247 struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
248 			      struct proc_dir_entry *de)
249 {
250 	struct inode *inode;
251 
252 	read_lock(&proc_subdir_lock);
253 	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
254 	if (de) {
255 		pde_get(de);
256 		read_unlock(&proc_subdir_lock);
257 		inode = proc_get_inode(dir->i_sb, de);
258 		if (!inode)
259 			return ERR_PTR(-ENOMEM);
260 		d_set_d_op(dentry, de->proc_dops);
261 		return d_splice_alias(inode, dentry);
262 	}
263 	read_unlock(&proc_subdir_lock);
264 	return ERR_PTR(-ENOENT);
265 }
266 
267 struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
268 		unsigned int flags)
269 {
270 	return proc_lookup_de(dir, dentry, PDE(dir));
271 }
272 
273 /*
274  * This returns non-zero if at EOF, so that the /proc
275  * root directory can use this and check if it should
276  * continue with the <pid> entries..
277  *
278  * Note that the VFS-layer doesn't care about the return
279  * value of the readdir() call, as long as it's non-negative
280  * for success..
281  */
282 int proc_readdir_de(struct file *file, struct dir_context *ctx,
283 		    struct proc_dir_entry *de)
284 {
285 	int i;
286 
287 	if (!dir_emit_dots(file, ctx))
288 		return 0;
289 
290 	i = ctx->pos - 2;
291 	read_lock(&proc_subdir_lock);
292 	de = pde_subdir_first(de);
293 	for (;;) {
294 		if (!de) {
295 			read_unlock(&proc_subdir_lock);
296 			return 0;
297 		}
298 		if (!i)
299 			break;
300 		de = pde_subdir_next(de);
301 		i--;
302 	}
303 
304 	do {
305 		struct proc_dir_entry *next;
306 		pde_get(de);
307 		read_unlock(&proc_subdir_lock);
308 		if (!dir_emit(ctx, de->name, de->namelen,
309 			    de->low_ino, de->mode >> 12)) {
310 			pde_put(de);
311 			return 0;
312 		}
313 		ctx->pos++;
314 		read_lock(&proc_subdir_lock);
315 		next = pde_subdir_next(de);
316 		pde_put(de);
317 		de = next;
318 	} while (de);
319 	read_unlock(&proc_subdir_lock);
320 	return 1;
321 }
322 
323 int proc_readdir(struct file *file, struct dir_context *ctx)
324 {
325 	struct inode *inode = file_inode(file);
326 
327 	return proc_readdir_de(file, ctx, PDE(inode));
328 }
329 
330 /*
331  * These are the generic /proc directory operations. They
332  * use the in-memory "struct proc_dir_entry" tree to parse
333  * the /proc directory.
334  */
335 static const struct file_operations proc_dir_operations = {
336 	.llseek			= generic_file_llseek,
337 	.read			= generic_read_dir,
338 	.iterate_shared		= proc_readdir,
339 };
340 
341 /*
342  * proc directories can do almost nothing..
343  */
344 static const struct inode_operations proc_dir_inode_operations = {
345 	.lookup		= proc_lookup,
346 	.getattr	= proc_getattr,
347 	.setattr	= proc_notify_change,
348 };
349 
350 /* returns the registered entry, or frees dp and returns NULL on failure */
351 struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
352 		struct proc_dir_entry *dp)
353 {
354 	if (proc_alloc_inum(&dp->low_ino))
355 		goto out_free_entry;
356 
357 	write_lock(&proc_subdir_lock);
358 	dp->parent = dir;
359 	if (pde_subdir_insert(dir, dp) == false) {
360 		WARN(1, "proc_dir_entry '%s/%s' already registered\n",
361 		     dir->name, dp->name);
362 		write_unlock(&proc_subdir_lock);
363 		goto out_free_inum;
364 	}
365 	write_unlock(&proc_subdir_lock);
366 
367 	return dp;
368 out_free_inum:
369 	proc_free_inum(dp->low_ino);
370 out_free_entry:
371 	pde_free(dp);
372 	return NULL;
373 }
374 
375 static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
376 					  const char *name,
377 					  umode_t mode,
378 					  nlink_t nlink)
379 {
380 	struct proc_dir_entry *ent = NULL;
381 	const char *fn;
382 	struct qstr qstr;
383 
384 	if (xlate_proc_name(name, parent, &fn) != 0)
385 		goto out;
386 	qstr.name = fn;
387 	qstr.len = strlen(fn);
388 	if (qstr.len == 0 || qstr.len >= 256) {
389 		WARN(1, "name len %u\n", qstr.len);
390 		return NULL;
391 	}
392 	if (qstr.len == 1 && fn[0] == '.') {
393 		WARN(1, "name '.'\n");
394 		return NULL;
395 	}
396 	if (qstr.len == 2 && fn[0] == '.' && fn[1] == '.') {
397 		WARN(1, "name '..'\n");
398 		return NULL;
399 	}
400 	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
401 		WARN(1, "create '/proc/%s' by hand\n", qstr.name);
402 		return NULL;
403 	}
404 	if (is_empty_pde(*parent)) {
405 		WARN(1, "attempt to add to permanently empty directory");
406 		return NULL;
407 	}
408 
409 	ent = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);
410 	if (!ent)
411 		goto out;
412 
413 	if (qstr.len + 1 <= SIZEOF_PDE_INLINE_NAME) {
414 		ent->name = ent->inline_name;
415 	} else {
416 		ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);
417 		if (!ent->name) {
418 			pde_free(ent);
419 			return NULL;
420 		}
421 	}
422 
423 	memcpy(ent->name, fn, qstr.len + 1);
424 	ent->namelen = qstr.len;
425 	ent->mode = mode;
426 	ent->nlink = nlink;
427 	ent->subdir = RB_ROOT;
428 	refcount_set(&ent->refcnt, 1);
429 	spin_lock_init(&ent->pde_unload_lock);
430 	INIT_LIST_HEAD(&ent->pde_openers);
431 	proc_set_user(ent, (*parent)->uid, (*parent)->gid);
432 
433 	ent->proc_dops = &proc_misc_dentry_ops;
434 
435 out:
436 	return ent;
437 }
438 
439 struct proc_dir_entry *proc_symlink(const char *name,
440 		struct proc_dir_entry *parent, const char *dest)
441 {
442 	struct proc_dir_entry *ent;
443 
444 	ent = __proc_create(&parent, name,
445 			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
446 
447 	if (ent) {
448 		ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
449 		if (ent->data) {
450 			strcpy((char*)ent->data,dest);
451 			ent->proc_iops = &proc_link_inode_operations;
452 			ent = proc_register(parent, ent);
453 		} else {
454 			pde_free(ent);
455 			ent = NULL;
456 		}
457 	}
458 	return ent;
459 }
460 EXPORT_SYMBOL(proc_symlink);
461 
462 struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
463 		struct proc_dir_entry *parent, void *data)
464 {
465 	struct proc_dir_entry *ent;
466 
467 	if (mode == 0)
468 		mode = S_IRUGO | S_IXUGO;
469 
470 	ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
471 	if (ent) {
472 		ent->data = data;
473 		ent->proc_fops = &proc_dir_operations;
474 		ent->proc_iops = &proc_dir_inode_operations;
475 		parent->nlink++;
476 		ent = proc_register(parent, ent);
477 		if (!ent)
478 			parent->nlink--;
479 	}
480 	return ent;
481 }
482 EXPORT_SYMBOL_GPL(proc_mkdir_data);
483 
484 struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
485 				       struct proc_dir_entry *parent)
486 {
487 	return proc_mkdir_data(name, mode, parent, NULL);
488 }
489 EXPORT_SYMBOL(proc_mkdir_mode);
490 
491 struct proc_dir_entry *proc_mkdir(const char *name,
492 		struct proc_dir_entry *parent)
493 {
494 	return proc_mkdir_data(name, 0, parent, NULL);
495 }
496 EXPORT_SYMBOL(proc_mkdir);
497 
498 struct proc_dir_entry *proc_create_mount_point(const char *name)
499 {
500 	umode_t mode = S_IFDIR | S_IRUGO | S_IXUGO;
501 	struct proc_dir_entry *ent, *parent = NULL;
502 
503 	ent = __proc_create(&parent, name, mode, 2);
504 	if (ent) {
505 		ent->data = NULL;
506 		ent->proc_fops = NULL;
507 		ent->proc_iops = NULL;
508 		parent->nlink++;
509 		ent = proc_register(parent, ent);
510 		if (!ent)
511 			parent->nlink--;
512 	}
513 	return ent;
514 }
515 EXPORT_SYMBOL(proc_create_mount_point);
516 
517 struct proc_dir_entry *proc_create_reg(const char *name, umode_t mode,
518 		struct proc_dir_entry **parent, void *data)
519 {
520 	struct proc_dir_entry *p;
521 
522 	if ((mode & S_IFMT) == 0)
523 		mode |= S_IFREG;
524 	if ((mode & S_IALLUGO) == 0)
525 		mode |= S_IRUGO;
526 	if (WARN_ON_ONCE(!S_ISREG(mode)))
527 		return NULL;
528 
529 	p = __proc_create(parent, name, mode, 1);
530 	if (p) {
531 		p->proc_iops = &proc_file_inode_operations;
532 		p->data = data;
533 	}
534 	return p;
535 }
536 
537 struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
538 		struct proc_dir_entry *parent,
539 		const struct file_operations *proc_fops, void *data)
540 {
541 	struct proc_dir_entry *p;
542 
543 	BUG_ON(proc_fops == NULL);
544 
545 	p = proc_create_reg(name, mode, &parent, data);
546 	if (!p)
547 		return NULL;
548 	p->proc_fops = proc_fops;
549 	return proc_register(parent, p);
550 }
551 EXPORT_SYMBOL(proc_create_data);
552 
553 struct proc_dir_entry *proc_create(const char *name, umode_t mode,
554 				   struct proc_dir_entry *parent,
555 				   const struct file_operations *proc_fops)
556 {
557 	return proc_create_data(name, mode, parent, proc_fops, NULL);
558 }
559 EXPORT_SYMBOL(proc_create);
560 
561 static int proc_seq_open(struct inode *inode, struct file *file)
562 {
563 	struct proc_dir_entry *de = PDE(inode);
564 
565 	if (de->state_size)
566 		return seq_open_private(file, de->seq_ops, de->state_size);
567 	return seq_open(file, de->seq_ops);
568 }
569 
570 static int proc_seq_release(struct inode *inode, struct file *file)
571 {
572 	struct proc_dir_entry *de = PDE(inode);
573 
574 	if (de->state_size)
575 		return seq_release_private(inode, file);
576 	return seq_release(inode, file);
577 }
578 
579 static const struct file_operations proc_seq_fops = {
580 	.open		= proc_seq_open,
581 	.read		= seq_read,
582 	.llseek		= seq_lseek,
583 	.release	= proc_seq_release,
584 };
585 
586 struct proc_dir_entry *proc_create_seq_private(const char *name, umode_t mode,
587 		struct proc_dir_entry *parent, const struct seq_operations *ops,
588 		unsigned int state_size, void *data)
589 {
590 	struct proc_dir_entry *p;
591 
592 	p = proc_create_reg(name, mode, &parent, data);
593 	if (!p)
594 		return NULL;
595 	p->proc_fops = &proc_seq_fops;
596 	p->seq_ops = ops;
597 	p->state_size = state_size;
598 	return proc_register(parent, p);
599 }
600 EXPORT_SYMBOL(proc_create_seq_private);
601 
602 static int proc_single_open(struct inode *inode, struct file *file)
603 {
604 	struct proc_dir_entry *de = PDE(inode);
605 
606 	return single_open(file, de->single_show, de->data);
607 }
608 
609 static const struct file_operations proc_single_fops = {
610 	.open		= proc_single_open,
611 	.read		= seq_read,
612 	.llseek		= seq_lseek,
613 	.release	= single_release,
614 };
615 
616 struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
617 		struct proc_dir_entry *parent,
618 		int (*show)(struct seq_file *, void *), void *data)
619 {
620 	struct proc_dir_entry *p;
621 
622 	p = proc_create_reg(name, mode, &parent, data);
623 	if (!p)
624 		return NULL;
625 	p->proc_fops = &proc_single_fops;
626 	p->single_show = show;
627 	return proc_register(parent, p);
628 }
629 EXPORT_SYMBOL(proc_create_single_data);
630 
631 void proc_set_size(struct proc_dir_entry *de, loff_t size)
632 {
633 	de->size = size;
634 }
635 EXPORT_SYMBOL(proc_set_size);
636 
637 void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
638 {
639 	de->uid = uid;
640 	de->gid = gid;
641 }
642 EXPORT_SYMBOL(proc_set_user);
643 
644 void pde_put(struct proc_dir_entry *pde)
645 {
646 	if (refcount_dec_and_test(&pde->refcnt)) {
647 		proc_free_inum(pde->low_ino);
648 		pde_free(pde);
649 	}
650 }
651 
652 /*
653  * Remove a /proc entry and free it if it's not currently in use.
654  */
655 void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
656 {
657 	struct proc_dir_entry *de = NULL;
658 	const char *fn = name;
659 	unsigned int len;
660 
661 	write_lock(&proc_subdir_lock);
662 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
663 		write_unlock(&proc_subdir_lock);
664 		return;
665 	}
666 	len = strlen(fn);
667 
668 	de = pde_subdir_find(parent, fn, len);
669 	if (de)
670 		rb_erase(&de->subdir_node, &parent->subdir);
671 	write_unlock(&proc_subdir_lock);
672 	if (!de) {
673 		WARN(1, "name '%s'\n", name);
674 		return;
675 	}
676 
677 	proc_entry_rundown(de);
678 
679 	if (S_ISDIR(de->mode))
680 		parent->nlink--;
681 	de->nlink = 0;
682 	WARN(pde_subdir_first(de),
683 	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",
684 	     __func__, de->parent->name, de->name, pde_subdir_first(de)->name);
685 	pde_put(de);
686 }
687 EXPORT_SYMBOL(remove_proc_entry);
688 
689 int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
690 {
691 	struct proc_dir_entry *root = NULL, *de, *next;
692 	const char *fn = name;
693 	unsigned int len;
694 
695 	write_lock(&proc_subdir_lock);
696 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
697 		write_unlock(&proc_subdir_lock);
698 		return -ENOENT;
699 	}
700 	len = strlen(fn);
701 
702 	root = pde_subdir_find(parent, fn, len);
703 	if (!root) {
704 		write_unlock(&proc_subdir_lock);
705 		return -ENOENT;
706 	}
707 	rb_erase(&root->subdir_node, &parent->subdir);
708 
709 	de = root;
710 	while (1) {
711 		next = pde_subdir_first(de);
712 		if (next) {
713 			rb_erase(&next->subdir_node, &de->subdir);
714 			de = next;
715 			continue;
716 		}
717 		write_unlock(&proc_subdir_lock);
718 
719 		proc_entry_rundown(de);
720 		next = de->parent;
721 		if (S_ISDIR(de->mode))
722 			next->nlink--;
723 		de->nlink = 0;
724 		if (de == root)
725 			break;
726 		pde_put(de);
727 
728 		write_lock(&proc_subdir_lock);
729 		de = next;
730 	}
731 	pde_put(root);
732 	return 0;
733 }
734 EXPORT_SYMBOL(remove_proc_subtree);
735 
736 void *proc_get_parent_data(const struct inode *inode)
737 {
738 	struct proc_dir_entry *de = PDE(inode);
739 	return de->parent->data;
740 }
741 EXPORT_SYMBOL_GPL(proc_get_parent_data);
742 
743 void proc_remove(struct proc_dir_entry *de)
744 {
745 	if (de)
746 		remove_proc_subtree(de->name, de->parent);
747 }
748 EXPORT_SYMBOL(proc_remove);
749 
750 void *PDE_DATA(const struct inode *inode)
751 {
752 	return __PDE_DATA(inode);
753 }
754 EXPORT_SYMBOL(PDE_DATA);
755 
756 /*
757  * Pull a user buffer into memory and pass it to the file's write handler if
758  * one is supplied.  The ->write() method is permitted to modify the
759  * kernel-side buffer.
760  */
761 ssize_t proc_simple_write(struct file *f, const char __user *ubuf, size_t size,
762 			  loff_t *_pos)
763 {
764 	struct proc_dir_entry *pde = PDE(file_inode(f));
765 	char *buf;
766 	int ret;
767 
768 	if (!pde->write)
769 		return -EACCES;
770 	if (size == 0 || size > PAGE_SIZE - 1)
771 		return -EINVAL;
772 	buf = memdup_user_nul(ubuf, size);
773 	if (IS_ERR(buf))
774 		return PTR_ERR(buf);
775 	ret = pde->write(f, buf, size);
776 	kfree(buf);
777 	return ret == 0 ? size : ret;
778 }
779