xref: /openbmc/linux/fs/proc/generic.c (revision 8e9356c6) 
1 /*
2  * proc/fs/generic.c --- generic routines for the proc-fs
3  *
4  * This file contains generic proc-fs routines for handling
5  * directories and files.
6  *
7  * Copyright (C) 1991, 1992 Linus Torvalds.
8  * Copyright (C) 1997 Theodore Ts'o
9  */
10 
11 #include <linux/errno.h>
12 #include <linux/time.h>
13 #include <linux/proc_fs.h>
14 #include <linux/stat.h>
15 #include <linux/mm.h>
16 #include <linux/module.h>
17 #include <linux/slab.h>
18 #include <linux/printk.h>
19 #include <linux/mount.h>
20 #include <linux/init.h>
21 #include <linux/idr.h>
22 #include <linux/namei.h>
23 #include <linux/bitops.h>
24 #include <linux/spinlock.h>
25 #include <linux/completion.h>
26 #include <asm/uaccess.h>
27 
28 #include "internal.h"
29 
30 DEFINE_SPINLOCK(proc_subdir_lock);
31 
32 static int proc_match(unsigned int len, const char *name, struct proc_dir_entry *de)
33 {
34 	if (de->namelen != len)
35 		return 0;
36 	return !memcmp(name, de->name, len);
37 }
38 
39 static int proc_notify_change(struct dentry *dentry, struct iattr *iattr)
40 {
41 	struct inode *inode = dentry->d_inode;
42 	struct proc_dir_entry *de = PDE(inode);
43 	int error;
44 
45 	error = inode_change_ok(inode, iattr);
46 	if (error)
47 		return error;
48 
49 	setattr_copy(inode, iattr);
50 	mark_inode_dirty(inode);
51 
52 	proc_set_user(de, inode->i_uid, inode->i_gid);
53 	de->mode = inode->i_mode;
54 	return 0;
55 }
56 
57 static int proc_getattr(struct vfsmount *mnt, struct dentry *dentry,
58 			struct kstat *stat)
59 {
60 	struct inode *inode = dentry->d_inode;
61 	struct proc_dir_entry *de = PROC_I(inode)->pde;
62 	if (de && de->nlink)
63 		set_nlink(inode, de->nlink);
64 
65 	generic_fillattr(inode, stat);
66 	return 0;
67 }
68 
69 static const struct inode_operations proc_file_inode_operations = {
70 	.setattr	= proc_notify_change,
71 };
72 
73 /*
74  * This function parses a name such as "tty/driver/serial", and
75  * returns the struct proc_dir_entry for "/proc/tty/driver", and
76  * returns "serial" in residual.
77  */
78 static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
79 			     const char **residual)
80 {
81 	const char     		*cp = name, *next;
82 	struct proc_dir_entry	*de;
83 	unsigned int		len;
84 
85 	de = *ret;
86 	if (!de)
87 		de = &proc_root;
88 
89 	while (1) {
90 		next = strchr(cp, '/');
91 		if (!next)
92 			break;
93 
94 		len = next - cp;
95 		for (de = de->subdir; de ; de = de->next) {
96 			if (proc_match(len, cp, de))
97 				break;
98 		}
99 		if (!de) {
100 			WARN(1, "name '%s'\n", name);
101 			return -ENOENT;
102 		}
103 		cp += len + 1;
104 	}
105 	*residual = cp;
106 	*ret = de;
107 	return 0;
108 }
109 
110 static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
111 			   const char **residual)
112 {
113 	int rv;
114 
115 	spin_lock(&proc_subdir_lock);
116 	rv = __xlate_proc_name(name, ret, residual);
117 	spin_unlock(&proc_subdir_lock);
118 	return rv;
119 }
120 
121 static DEFINE_IDA(proc_inum_ida);
122 static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */
123 
124 #define PROC_DYNAMIC_FIRST 0xF0000000U
125 
126 /*
127  * Return an inode number between PROC_DYNAMIC_FIRST and
128  * 0xffffffff, or zero on failure.
129  */
130 int proc_alloc_inum(unsigned int *inum)
131 {
132 	unsigned int i;
133 	int error;
134 
135 retry:
136 	if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL))
137 		return -ENOMEM;
138 
139 	spin_lock_irq(&proc_inum_lock);
140 	error = ida_get_new(&proc_inum_ida, &i);
141 	spin_unlock_irq(&proc_inum_lock);
142 	if (error == -EAGAIN)
143 		goto retry;
144 	else if (error)
145 		return error;
146 
147 	if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
148 		spin_lock_irq(&proc_inum_lock);
149 		ida_remove(&proc_inum_ida, i);
150 		spin_unlock_irq(&proc_inum_lock);
151 		return -ENOSPC;
152 	}
153 	*inum = PROC_DYNAMIC_FIRST + i;
154 	return 0;
155 }
156 
157 void proc_free_inum(unsigned int inum)
158 {
159 	unsigned long flags;
160 	spin_lock_irqsave(&proc_inum_lock, flags);
161 	ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
162 	spin_unlock_irqrestore(&proc_inum_lock, flags);
163 }
164 
165 static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
166 {
167 	nd_set_link(nd, __PDE_DATA(dentry->d_inode));
168 	return NULL;
169 }
170 
171 static const struct inode_operations proc_link_inode_operations = {
172 	.readlink	= generic_readlink,
173 	.follow_link	= proc_follow_link,
174 };
175 
176 /*
177  * Don't create negative dentries here, return -ENOENT by hand
178  * instead.
179  */
180 struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
181 		struct dentry *dentry)
182 {
183 	struct inode *inode;
184 
185 	spin_lock(&proc_subdir_lock);
186 	for (de = de->subdir; de ; de = de->next) {
187 		if (de->namelen != dentry->d_name.len)
188 			continue;
189 		if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
190 			pde_get(de);
191 			spin_unlock(&proc_subdir_lock);
192 			inode = proc_get_inode(dir->i_sb, de);
193 			if (!inode)
194 				return ERR_PTR(-ENOMEM);
195 			d_set_d_op(dentry, &simple_dentry_operations);
196 			d_add(dentry, inode);
197 			return NULL;
198 		}
199 	}
200 	spin_unlock(&proc_subdir_lock);
201 	return ERR_PTR(-ENOENT);
202 }
203 
204 struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
205 		unsigned int flags)
206 {
207 	return proc_lookup_de(PDE(dir), dir, dentry);
208 }
209 
210 /*
211  * This returns non-zero if at EOF, so that the /proc
212  * root directory can use this and check if it should
213  * continue with the <pid> entries..
214  *
215  * Note that the VFS-layer doesn't care about the return
216  * value of the readdir() call, as long as it's non-negative
217  * for success..
218  */
219 int proc_readdir_de(struct proc_dir_entry *de, struct file *file,
220 		    struct dir_context *ctx)
221 {
222 	int i;
223 
224 	if (!dir_emit_dots(file, ctx))
225 		return 0;
226 
227 	spin_lock(&proc_subdir_lock);
228 	de = de->subdir;
229 	i = ctx->pos - 2;
230 	for (;;) {
231 		if (!de) {
232 			spin_unlock(&proc_subdir_lock);
233 			return 0;
234 		}
235 		if (!i)
236 			break;
237 		de = de->next;
238 		i--;
239 	}
240 
241 	do {
242 		struct proc_dir_entry *next;
243 		pde_get(de);
244 		spin_unlock(&proc_subdir_lock);
245 		if (!dir_emit(ctx, de->name, de->namelen,
246 			    de->low_ino, de->mode >> 12)) {
247 			pde_put(de);
248 			return 0;
249 		}
250 		spin_lock(&proc_subdir_lock);
251 		ctx->pos++;
252 		next = de->next;
253 		pde_put(de);
254 		de = next;
255 	} while (de);
256 	spin_unlock(&proc_subdir_lock);
257 	return 1;
258 }
259 
260 int proc_readdir(struct file *file, struct dir_context *ctx)
261 {
262 	struct inode *inode = file_inode(file);
263 
264 	return proc_readdir_de(PDE(inode), file, ctx);
265 }
266 
267 /*
268  * These are the generic /proc directory operations. They
269  * use the in-memory "struct proc_dir_entry" tree to parse
270  * the /proc directory.
271  */
272 static const struct file_operations proc_dir_operations = {
273 	.llseek			= generic_file_llseek,
274 	.read			= generic_read_dir,
275 	.iterate		= proc_readdir,
276 };
277 
278 /*
279  * proc directories can do almost nothing..
280  */
281 static const struct inode_operations proc_dir_inode_operations = {
282 	.lookup		= proc_lookup,
283 	.getattr	= proc_getattr,
284 	.setattr	= proc_notify_change,
285 };
286 
287 static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)
288 {
289 	struct proc_dir_entry *tmp;
290 	int ret;
291 
292 	ret = proc_alloc_inum(&dp->low_ino);
293 	if (ret)
294 		return ret;
295 
296 	if (S_ISDIR(dp->mode)) {
297 		dp->proc_fops = &proc_dir_operations;
298 		dp->proc_iops = &proc_dir_inode_operations;
299 		dir->nlink++;
300 	} else if (S_ISLNK(dp->mode)) {
301 		dp->proc_iops = &proc_link_inode_operations;
302 	} else if (S_ISREG(dp->mode)) {
303 		BUG_ON(dp->proc_fops == NULL);
304 		dp->proc_iops = &proc_file_inode_operations;
305 	} else {
306 		WARN_ON(1);
307 		return -EINVAL;
308 	}
309 
310 	spin_lock(&proc_subdir_lock);
311 
312 	for (tmp = dir->subdir; tmp; tmp = tmp->next)
313 		if (strcmp(tmp->name, dp->name) == 0) {
314 			WARN(1, "proc_dir_entry '%s/%s' already registered\n",
315 				dir->name, dp->name);
316 			break;
317 		}
318 
319 	dp->next = dir->subdir;
320 	dp->parent = dir;
321 	dir->subdir = dp;
322 	spin_unlock(&proc_subdir_lock);
323 
324 	return 0;
325 }
326 
327 static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
328 					  const char *name,
329 					  umode_t mode,
330 					  nlink_t nlink)
331 {
332 	struct proc_dir_entry *ent = NULL;
333 	const char *fn = name;
334 	unsigned int len;
335 
336 	/* make sure name is valid */
337 	if (!name || !strlen(name))
338 		goto out;
339 
340 	if (xlate_proc_name(name, parent, &fn) != 0)
341 		goto out;
342 
343 	/* At this point there must not be any '/' characters beyond *fn */
344 	if (strchr(fn, '/'))
345 		goto out;
346 
347 	len = strlen(fn);
348 
349 	ent = kzalloc(sizeof(struct proc_dir_entry) + len + 1, GFP_KERNEL);
350 	if (!ent)
351 		goto out;
352 
353 	memcpy(ent->name, fn, len + 1);
354 	ent->namelen = len;
355 	ent->mode = mode;
356 	ent->nlink = nlink;
357 	atomic_set(&ent->count, 1);
358 	spin_lock_init(&ent->pde_unload_lock);
359 	INIT_LIST_HEAD(&ent->pde_openers);
360 out:
361 	return ent;
362 }
363 
364 struct proc_dir_entry *proc_symlink(const char *name,
365 		struct proc_dir_entry *parent, const char *dest)
366 {
367 	struct proc_dir_entry *ent;
368 
369 	ent = __proc_create(&parent, name,
370 			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
371 
372 	if (ent) {
373 		ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
374 		if (ent->data) {
375 			strcpy((char*)ent->data,dest);
376 			if (proc_register(parent, ent) < 0) {
377 				kfree(ent->data);
378 				kfree(ent);
379 				ent = NULL;
380 			}
381 		} else {
382 			kfree(ent);
383 			ent = NULL;
384 		}
385 	}
386 	return ent;
387 }
388 EXPORT_SYMBOL(proc_symlink);
389 
390 struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
391 		struct proc_dir_entry *parent, void *data)
392 {
393 	struct proc_dir_entry *ent;
394 
395 	if (mode == 0)
396 		mode = S_IRUGO | S_IXUGO;
397 
398 	ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
399 	if (ent) {
400 		ent->data = data;
401 		if (proc_register(parent, ent) < 0) {
402 			kfree(ent);
403 			ent = NULL;
404 		}
405 	}
406 	return ent;
407 }
408 EXPORT_SYMBOL_GPL(proc_mkdir_data);
409 
410 struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
411 				       struct proc_dir_entry *parent)
412 {
413 	return proc_mkdir_data(name, mode, parent, NULL);
414 }
415 EXPORT_SYMBOL(proc_mkdir_mode);
416 
417 struct proc_dir_entry *proc_mkdir(const char *name,
418 		struct proc_dir_entry *parent)
419 {
420 	return proc_mkdir_data(name, 0, parent, NULL);
421 }
422 EXPORT_SYMBOL(proc_mkdir);
423 
424 struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
425 					struct proc_dir_entry *parent,
426 					const struct file_operations *proc_fops,
427 					void *data)
428 {
429 	struct proc_dir_entry *pde;
430 	if ((mode & S_IFMT) == 0)
431 		mode |= S_IFREG;
432 
433 	if (!S_ISREG(mode)) {
434 		WARN_ON(1);	/* use proc_mkdir() */
435 		return NULL;
436 	}
437 
438 	if ((mode & S_IALLUGO) == 0)
439 		mode |= S_IRUGO;
440 	pde = __proc_create(&parent, name, mode, 1);
441 	if (!pde)
442 		goto out;
443 	pde->proc_fops = proc_fops;
444 	pde->data = data;
445 	if (proc_register(parent, pde) < 0)
446 		goto out_free;
447 	return pde;
448 out_free:
449 	kfree(pde);
450 out:
451 	return NULL;
452 }
453 EXPORT_SYMBOL(proc_create_data);
454 
455 void proc_set_size(struct proc_dir_entry *de, loff_t size)
456 {
457 	de->size = size;
458 }
459 EXPORT_SYMBOL(proc_set_size);
460 
461 void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
462 {
463 	de->uid = uid;
464 	de->gid = gid;
465 }
466 EXPORT_SYMBOL(proc_set_user);
467 
468 static void free_proc_entry(struct proc_dir_entry *de)
469 {
470 	proc_free_inum(de->low_ino);
471 
472 	if (S_ISLNK(de->mode))
473 		kfree(de->data);
474 	kfree(de);
475 }
476 
477 void pde_put(struct proc_dir_entry *pde)
478 {
479 	if (atomic_dec_and_test(&pde->count))
480 		free_proc_entry(pde);
481 }
482 
483 /*
484  * Remove a /proc entry and free it if it's not currently in use.
485  */
486 void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
487 {
488 	struct proc_dir_entry **p;
489 	struct proc_dir_entry *de = NULL;
490 	const char *fn = name;
491 	unsigned int len;
492 
493 	spin_lock(&proc_subdir_lock);
494 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
495 		spin_unlock(&proc_subdir_lock);
496 		return;
497 	}
498 	len = strlen(fn);
499 
500 	for (p = &parent->subdir; *p; p=&(*p)->next ) {
501 		if (proc_match(len, fn, *p)) {
502 			de = *p;
503 			*p = de->next;
504 			de->next = NULL;
505 			break;
506 		}
507 	}
508 	spin_unlock(&proc_subdir_lock);
509 	if (!de) {
510 		WARN(1, "name '%s'\n", name);
511 		return;
512 	}
513 
514 	proc_entry_rundown(de);
515 
516 	if (S_ISDIR(de->mode))
517 		parent->nlink--;
518 	de->nlink = 0;
519 	WARN(de->subdir, "%s: removing non-empty directory "
520 			 "'%s/%s', leaking at least '%s'\n", __func__,
521 			 de->parent->name, de->name, de->subdir->name);
522 	pde_put(de);
523 }
524 EXPORT_SYMBOL(remove_proc_entry);
525 
526 int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
527 {
528 	struct proc_dir_entry **p;
529 	struct proc_dir_entry *root = NULL, *de, *next;
530 	const char *fn = name;
531 	unsigned int len;
532 
533 	spin_lock(&proc_subdir_lock);
534 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
535 		spin_unlock(&proc_subdir_lock);
536 		return -ENOENT;
537 	}
538 	len = strlen(fn);
539 
540 	for (p = &parent->subdir; *p; p=&(*p)->next ) {
541 		if (proc_match(len, fn, *p)) {
542 			root = *p;
543 			*p = root->next;
544 			root->next = NULL;
545 			break;
546 		}
547 	}
548 	if (!root) {
549 		spin_unlock(&proc_subdir_lock);
550 		return -ENOENT;
551 	}
552 	de = root;
553 	while (1) {
554 		next = de->subdir;
555 		if (next) {
556 			de->subdir = next->next;
557 			next->next = NULL;
558 			de = next;
559 			continue;
560 		}
561 		spin_unlock(&proc_subdir_lock);
562 
563 		proc_entry_rundown(de);
564 		next = de->parent;
565 		if (S_ISDIR(de->mode))
566 			next->nlink--;
567 		de->nlink = 0;
568 		if (de == root)
569 			break;
570 		pde_put(de);
571 
572 		spin_lock(&proc_subdir_lock);
573 		de = next;
574 	}
575 	pde_put(root);
576 	return 0;
577 }
578 EXPORT_SYMBOL(remove_proc_subtree);
579 
580 void *proc_get_parent_data(const struct inode *inode)
581 {
582 	struct proc_dir_entry *de = PDE(inode);
583 	return de->parent->data;
584 }
585 EXPORT_SYMBOL_GPL(proc_get_parent_data);
586 
587 void proc_remove(struct proc_dir_entry *de)
588 {
589 	if (de)
590 		remove_proc_subtree(de->name, de->parent);
591 }
592 EXPORT_SYMBOL(proc_remove);
593 
594 void *PDE_DATA(const struct inode *inode)
595 {
596 	return __PDE_DATA(inode);
597 }
598 EXPORT_SYMBOL(PDE_DATA);
599