xref: /openbmc/linux/fs/proc/generic.c (revision 77d84ff8) 
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 	de->uid = inode->i_uid;
53 	de->gid = inode->i_gid;
54 	de->mode = inode->i_mode;
55 	return 0;
56 }
57 
58 static int proc_getattr(struct vfsmount *mnt, struct dentry *dentry,
59 			struct kstat *stat)
60 {
61 	struct inode *inode = dentry->d_inode;
62 	struct proc_dir_entry *de = PROC_I(inode)->pde;
63 	if (de && de->nlink)
64 		set_nlink(inode, de->nlink);
65 
66 	generic_fillattr(inode, stat);
67 	return 0;
68 }
69 
70 static const struct inode_operations proc_file_inode_operations = {
71 	.setattr	= proc_notify_change,
72 };
73 
74 /*
75  * This function parses a name such as "tty/driver/serial", and
76  * returns the struct proc_dir_entry for "/proc/tty/driver", and
77  * returns "serial" in residual.
78  */
79 static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
80 			     const char **residual)
81 {
82 	const char     		*cp = name, *next;
83 	struct proc_dir_entry	*de;
84 	unsigned int		len;
85 
86 	de = *ret;
87 	if (!de)
88 		de = &proc_root;
89 
90 	while (1) {
91 		next = strchr(cp, '/');
92 		if (!next)
93 			break;
94 
95 		len = next - cp;
96 		for (de = de->subdir; de ; de = de->next) {
97 			if (proc_match(len, cp, de))
98 				break;
99 		}
100 		if (!de) {
101 			WARN(1, "name '%s'\n", name);
102 			return -ENOENT;
103 		}
104 		cp += len + 1;
105 	}
106 	*residual = cp;
107 	*ret = de;
108 	return 0;
109 }
110 
111 static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
112 			   const char **residual)
113 {
114 	int rv;
115 
116 	spin_lock(&proc_subdir_lock);
117 	rv = __xlate_proc_name(name, ret, residual);
118 	spin_unlock(&proc_subdir_lock);
119 	return rv;
120 }
121 
122 static DEFINE_IDA(proc_inum_ida);
123 static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */
124 
125 #define PROC_DYNAMIC_FIRST 0xF0000000U
126 
127 /*
128  * Return an inode number between PROC_DYNAMIC_FIRST and
129  * 0xffffffff, or zero on failure.
130  */
131 int proc_alloc_inum(unsigned int *inum)
132 {
133 	unsigned int i;
134 	int error;
135 
136 retry:
137 	if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL))
138 		return -ENOMEM;
139 
140 	spin_lock_irq(&proc_inum_lock);
141 	error = ida_get_new(&proc_inum_ida, &i);
142 	spin_unlock_irq(&proc_inum_lock);
143 	if (error == -EAGAIN)
144 		goto retry;
145 	else if (error)
146 		return error;
147 
148 	if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
149 		spin_lock_irq(&proc_inum_lock);
150 		ida_remove(&proc_inum_ida, i);
151 		spin_unlock_irq(&proc_inum_lock);
152 		return -ENOSPC;
153 	}
154 	*inum = PROC_DYNAMIC_FIRST + i;
155 	return 0;
156 }
157 
158 void proc_free_inum(unsigned int inum)
159 {
160 	unsigned long flags;
161 	spin_lock_irqsave(&proc_inum_lock, flags);
162 	ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
163 	spin_unlock_irqrestore(&proc_inum_lock, flags);
164 }
165 
166 static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
167 {
168 	nd_set_link(nd, __PDE_DATA(dentry->d_inode));
169 	return NULL;
170 }
171 
172 static const struct inode_operations proc_link_inode_operations = {
173 	.readlink	= generic_readlink,
174 	.follow_link	= proc_follow_link,
175 };
176 
177 /*
178  * Don't create negative dentries here, return -ENOENT by hand
179  * instead.
180  */
181 struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
182 		struct dentry *dentry)
183 {
184 	struct inode *inode;
185 
186 	spin_lock(&proc_subdir_lock);
187 	for (de = de->subdir; de ; de = de->next) {
188 		if (de->namelen != dentry->d_name.len)
189 			continue;
190 		if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
191 			pde_get(de);
192 			spin_unlock(&proc_subdir_lock);
193 			inode = proc_get_inode(dir->i_sb, de);
194 			if (!inode)
195 				return ERR_PTR(-ENOMEM);
196 			d_set_d_op(dentry, &simple_dentry_operations);
197 			d_add(dentry, inode);
198 			return NULL;
199 		}
200 	}
201 	spin_unlock(&proc_subdir_lock);
202 	return ERR_PTR(-ENOENT);
203 }
204 
205 struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
206 		unsigned int flags)
207 {
208 	return proc_lookup_de(PDE(dir), dir, dentry);
209 }
210 
211 /*
212  * This returns non-zero if at EOF, so that the /proc
213  * root directory can use this and check if it should
214  * continue with the <pid> entries..
215  *
216  * Note that the VFS-layer doesn't care about the return
217  * value of the readdir() call, as long as it's non-negative
218  * for success..
219  */
220 int proc_readdir_de(struct proc_dir_entry *de, struct file *file,
221 		    struct dir_context *ctx)
222 {
223 	int i;
224 
225 	if (!dir_emit_dots(file, ctx))
226 		return 0;
227 
228 	spin_lock(&proc_subdir_lock);
229 	de = de->subdir;
230 	i = ctx->pos - 2;
231 	for (;;) {
232 		if (!de) {
233 			spin_unlock(&proc_subdir_lock);
234 			return 0;
235 		}
236 		if (!i)
237 			break;
238 		de = de->next;
239 		i--;
240 	}
241 
242 	do {
243 		struct proc_dir_entry *next;
244 		pde_get(de);
245 		spin_unlock(&proc_subdir_lock);
246 		if (!dir_emit(ctx, de->name, de->namelen,
247 			    de->low_ino, de->mode >> 12)) {
248 			pde_put(de);
249 			return 0;
250 		}
251 		spin_lock(&proc_subdir_lock);
252 		ctx->pos++;
253 		next = de->next;
254 		pde_put(de);
255 		de = next;
256 	} while (de);
257 	spin_unlock(&proc_subdir_lock);
258 	return 1;
259 }
260 
261 int proc_readdir(struct file *file, struct dir_context *ctx)
262 {
263 	struct inode *inode = file_inode(file);
264 
265 	return proc_readdir_de(PDE(inode), file, ctx);
266 }
267 
268 /*
269  * These are the generic /proc directory operations. They
270  * use the in-memory "struct proc_dir_entry" tree to parse
271  * the /proc directory.
272  */
273 static const struct file_operations proc_dir_operations = {
274 	.llseek			= generic_file_llseek,
275 	.read			= generic_read_dir,
276 	.iterate		= proc_readdir,
277 };
278 
279 /*
280  * proc directories can do almost nothing..
281  */
282 static const struct inode_operations proc_dir_inode_operations = {
283 	.lookup		= proc_lookup,
284 	.getattr	= proc_getattr,
285 	.setattr	= proc_notify_change,
286 };
287 
288 static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)
289 {
290 	struct proc_dir_entry *tmp;
291 	int ret;
292 
293 	ret = proc_alloc_inum(&dp->low_ino);
294 	if (ret)
295 		return ret;
296 
297 	if (S_ISDIR(dp->mode)) {
298 		dp->proc_fops = &proc_dir_operations;
299 		dp->proc_iops = &proc_dir_inode_operations;
300 		dir->nlink++;
301 	} else if (S_ISLNK(dp->mode)) {
302 		dp->proc_iops = &proc_link_inode_operations;
303 	} else if (S_ISREG(dp->mode)) {
304 		BUG_ON(dp->proc_fops == NULL);
305 		dp->proc_iops = &proc_file_inode_operations;
306 	} else {
307 		WARN_ON(1);
308 		return -EINVAL;
309 	}
310 
311 	spin_lock(&proc_subdir_lock);
312 
313 	for (tmp = dir->subdir; tmp; tmp = tmp->next)
314 		if (strcmp(tmp->name, dp->name) == 0) {
315 			WARN(1, "proc_dir_entry '%s/%s' already registered\n",
316 				dir->name, dp->name);
317 			break;
318 		}
319 
320 	dp->next = dir->subdir;
321 	dp->parent = dir;
322 	dir->subdir = dp;
323 	spin_unlock(&proc_subdir_lock);
324 
325 	return 0;
326 }
327 
328 static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
329 					  const char *name,
330 					  umode_t mode,
331 					  nlink_t nlink)
332 {
333 	struct proc_dir_entry *ent = NULL;
334 	const char *fn = name;
335 	unsigned int len;
336 
337 	/* make sure name is valid */
338 	if (!name || !strlen(name))
339 		goto out;
340 
341 	if (xlate_proc_name(name, parent, &fn) != 0)
342 		goto out;
343 
344 	/* At this point there must not be any '/' characters beyond *fn */
345 	if (strchr(fn, '/'))
346 		goto out;
347 
348 	len = strlen(fn);
349 
350 	ent = kzalloc(sizeof(struct proc_dir_entry) + len + 1, GFP_KERNEL);
351 	if (!ent)
352 		goto out;
353 
354 	memcpy(ent->name, fn, len + 1);
355 	ent->namelen = len;
356 	ent->mode = mode;
357 	ent->nlink = nlink;
358 	atomic_set(&ent->count, 1);
359 	spin_lock_init(&ent->pde_unload_lock);
360 	INIT_LIST_HEAD(&ent->pde_openers);
361 out:
362 	return ent;
363 }
364 
365 struct proc_dir_entry *proc_symlink(const char *name,
366 		struct proc_dir_entry *parent, const char *dest)
367 {
368 	struct proc_dir_entry *ent;
369 
370 	ent = __proc_create(&parent, name,
371 			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
372 
373 	if (ent) {
374 		ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
375 		if (ent->data) {
376 			strcpy((char*)ent->data,dest);
377 			if (proc_register(parent, ent) < 0) {
378 				kfree(ent->data);
379 				kfree(ent);
380 				ent = NULL;
381 			}
382 		} else {
383 			kfree(ent);
384 			ent = NULL;
385 		}
386 	}
387 	return ent;
388 }
389 EXPORT_SYMBOL(proc_symlink);
390 
391 struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
392 		struct proc_dir_entry *parent, void *data)
393 {
394 	struct proc_dir_entry *ent;
395 
396 	if (mode == 0)
397 		mode = S_IRUGO | S_IXUGO;
398 
399 	ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
400 	if (ent) {
401 		ent->data = data;
402 		if (proc_register(parent, ent) < 0) {
403 			kfree(ent);
404 			ent = NULL;
405 		}
406 	}
407 	return ent;
408 }
409 EXPORT_SYMBOL_GPL(proc_mkdir_data);
410 
411 struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
412 				       struct proc_dir_entry *parent)
413 {
414 	return proc_mkdir_data(name, mode, parent, NULL);
415 }
416 EXPORT_SYMBOL(proc_mkdir_mode);
417 
418 struct proc_dir_entry *proc_mkdir(const char *name,
419 		struct proc_dir_entry *parent)
420 {
421 	return proc_mkdir_data(name, 0, parent, NULL);
422 }
423 EXPORT_SYMBOL(proc_mkdir);
424 
425 struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
426 					struct proc_dir_entry *parent,
427 					const struct file_operations *proc_fops,
428 					void *data)
429 {
430 	struct proc_dir_entry *pde;
431 	if ((mode & S_IFMT) == 0)
432 		mode |= S_IFREG;
433 
434 	if (!S_ISREG(mode)) {
435 		WARN_ON(1);	/* use proc_mkdir() */
436 		return NULL;
437 	}
438 
439 	if ((mode & S_IALLUGO) == 0)
440 		mode |= S_IRUGO;
441 	pde = __proc_create(&parent, name, mode, 1);
442 	if (!pde)
443 		goto out;
444 	pde->proc_fops = proc_fops;
445 	pde->data = data;
446 	if (proc_register(parent, pde) < 0)
447 		goto out_free;
448 	return pde;
449 out_free:
450 	kfree(pde);
451 out:
452 	return NULL;
453 }
454 EXPORT_SYMBOL(proc_create_data);
455 
456 void proc_set_size(struct proc_dir_entry *de, loff_t size)
457 {
458 	de->size = size;
459 }
460 EXPORT_SYMBOL(proc_set_size);
461 
462 void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
463 {
464 	de->uid = uid;
465 	de->gid = gid;
466 }
467 EXPORT_SYMBOL(proc_set_user);
468 
469 static void free_proc_entry(struct proc_dir_entry *de)
470 {
471 	proc_free_inum(de->low_ino);
472 
473 	if (S_ISLNK(de->mode))
474 		kfree(de->data);
475 	kfree(de);
476 }
477 
478 void pde_put(struct proc_dir_entry *pde)
479 {
480 	if (atomic_dec_and_test(&pde->count))
481 		free_proc_entry(pde);
482 }
483 
484 /*
485  * Remove a /proc entry and free it if it's not currently in use.
486  */
487 void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
488 {
489 	struct proc_dir_entry **p;
490 	struct proc_dir_entry *de = NULL;
491 	const char *fn = name;
492 	unsigned int len;
493 
494 	spin_lock(&proc_subdir_lock);
495 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
496 		spin_unlock(&proc_subdir_lock);
497 		return;
498 	}
499 	len = strlen(fn);
500 
501 	for (p = &parent->subdir; *p; p=&(*p)->next ) {
502 		if (proc_match(len, fn, *p)) {
503 			de = *p;
504 			*p = de->next;
505 			de->next = NULL;
506 			break;
507 		}
508 	}
509 	spin_unlock(&proc_subdir_lock);
510 	if (!de) {
511 		WARN(1, "name '%s'\n", name);
512 		return;
513 	}
514 
515 	proc_entry_rundown(de);
516 
517 	if (S_ISDIR(de->mode))
518 		parent->nlink--;
519 	de->nlink = 0;
520 	WARN(de->subdir, "%s: removing non-empty directory "
521 			 "'%s/%s', leaking at least '%s'\n", __func__,
522 			 de->parent->name, de->name, de->subdir->name);
523 	pde_put(de);
524 }
525 EXPORT_SYMBOL(remove_proc_entry);
526 
527 int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
528 {
529 	struct proc_dir_entry **p;
530 	struct proc_dir_entry *root = NULL, *de, *next;
531 	const char *fn = name;
532 	unsigned int len;
533 
534 	spin_lock(&proc_subdir_lock);
535 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
536 		spin_unlock(&proc_subdir_lock);
537 		return -ENOENT;
538 	}
539 	len = strlen(fn);
540 
541 	for (p = &parent->subdir; *p; p=&(*p)->next ) {
542 		if (proc_match(len, fn, *p)) {
543 			root = *p;
544 			*p = root->next;
545 			root->next = NULL;
546 			break;
547 		}
548 	}
549 	if (!root) {
550 		spin_unlock(&proc_subdir_lock);
551 		return -ENOENT;
552 	}
553 	de = root;
554 	while (1) {
555 		next = de->subdir;
556 		if (next) {
557 			de->subdir = next->next;
558 			next->next = NULL;
559 			de = next;
560 			continue;
561 		}
562 		spin_unlock(&proc_subdir_lock);
563 
564 		proc_entry_rundown(de);
565 		next = de->parent;
566 		if (S_ISDIR(de->mode))
567 			next->nlink--;
568 		de->nlink = 0;
569 		if (de == root)
570 			break;
571 		pde_put(de);
572 
573 		spin_lock(&proc_subdir_lock);
574 		de = next;
575 	}
576 	pde_put(root);
577 	return 0;
578 }
579 EXPORT_SYMBOL(remove_proc_subtree);
580 
581 void *proc_get_parent_data(const struct inode *inode)
582 {
583 	struct proc_dir_entry *de = PDE(inode);
584 	return de->parent->data;
585 }
586 EXPORT_SYMBOL_GPL(proc_get_parent_data);
587 
588 void proc_remove(struct proc_dir_entry *de)
589 {
590 	if (de)
591 		remove_proc_subtree(de->name, de->parent);
592 }
593 EXPORT_SYMBOL(proc_remove);
594 
595 void *PDE_DATA(const struct inode *inode)
596 {
597 	return __PDE_DATA(inode);
598 }
599 EXPORT_SYMBOL(PDE_DATA);
600