xref: /linux/fs/seq_file.c (revision a5766f11cfd3a0c03450d99c8fe548c2940be884) 
1 /*
2  * linux/fs/seq_file.c
3  *
4  * helper functions for making synthetic files from sequences of records.
5  * initial implementation -- AV, Oct 2001.
6  */
7 
8 #include <linux/fs.h>
9 #include <linux/module.h>
10 #include <linux/seq_file.h>
11 #include <linux/slab.h>
12 
13 #include <asm/uaccess.h>
14 #include <asm/page.h>
15 
16 /**
17  *	seq_open -	initialize sequential file
18  *	@file: file we initialize
19  *	@op: method table describing the sequence
20  *
21  *	seq_open() sets @file, associating it with a sequence described
22  *	by @op.  @op->start() sets the iterator up and returns the first
23  *	element of sequence. @op->stop() shuts it down.  @op->next()
24  *	returns the next element of sequence.  @op->show() prints element
25  *	into the buffer.  In case of error ->start() and ->next() return
26  *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
27  *	returns 0 in case of success and negative number in case of error.
28  *	Returning SEQ_SKIP means "discard this element and move on".
29  */
30 int seq_open(struct file *file, const struct seq_operations *op)
31 {
32 	struct seq_file *p = file->private_data;
33 
34 	if (!p) {
35 		p = kmalloc(sizeof(*p), GFP_KERNEL);
36 		if (!p)
37 			return -ENOMEM;
38 		file->private_data = p;
39 	}
40 	memset(p, 0, sizeof(*p));
41 	mutex_init(&p->lock);
42 	p->op = op;
43 
44 	/*
45 	 * Wrappers around seq_open(e.g. swaps_open) need to be
46 	 * aware of this. If they set f_version themselves, they
47 	 * should call seq_open first and then set f_version.
48 	 */
49 	file->f_version = 0;
50 
51 	/* SEQ files support lseek, but not pread/pwrite */
52 	file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
53 	return 0;
54 }
55 EXPORT_SYMBOL(seq_open);
56 
57 /**
58  *	seq_read -	->read() method for sequential files.
59  *	@file: the file to read from
60  *	@buf: the buffer to read to
61  *	@size: the maximum number of bytes to read
62  *	@ppos: the current position in the file
63  *
64  *	Ready-made ->f_op->read()
65  */
66 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
67 {
68 	struct seq_file *m = (struct seq_file *)file->private_data;
69 	size_t copied = 0;
70 	loff_t pos;
71 	size_t n;
72 	void *p;
73 	int err = 0;
74 
75 	mutex_lock(&m->lock);
76 	/*
77 	 * seq_file->op->..m_start/m_stop/m_next may do special actions
78 	 * or optimisations based on the file->f_version, so we want to
79 	 * pass the file->f_version to those methods.
80 	 *
81 	 * seq_file->version is just copy of f_version, and seq_file
82 	 * methods can treat it simply as file version.
83 	 * It is copied in first and copied out after all operations.
84 	 * It is convenient to have it as  part of structure to avoid the
85 	 * need of passing another argument to all the seq_file methods.
86 	 */
87 	m->version = file->f_version;
88 	/* grab buffer if we didn't have one */
89 	if (!m->buf) {
90 		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
91 		if (!m->buf)
92 			goto Enomem;
93 	}
94 	/* if not empty - flush it first */
95 	if (m->count) {
96 		n = min(m->count, size);
97 		err = copy_to_user(buf, m->buf + m->from, n);
98 		if (err)
99 			goto Efault;
100 		m->count -= n;
101 		m->from += n;
102 		size -= n;
103 		buf += n;
104 		copied += n;
105 		if (!m->count)
106 			m->index++;
107 		if (!size)
108 			goto Done;
109 	}
110 	/* we need at least one record in buffer */
111 	pos = m->index;
112 	p = m->op->start(m, &pos);
113 	while (1) {
114 		err = PTR_ERR(p);
115 		if (!p || IS_ERR(p))
116 			break;
117 		err = m->op->show(m, p);
118 		if (err < 0)
119 			break;
120 		if (unlikely(err))
121 			m->count = 0;
122 		if (unlikely(!m->count)) {
123 			p = m->op->next(m, p, &pos);
124 			m->index = pos;
125 			continue;
126 		}
127 		if (m->count < m->size)
128 			goto Fill;
129 		m->op->stop(m, p);
130 		kfree(m->buf);
131 		m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
132 		if (!m->buf)
133 			goto Enomem;
134 		m->count = 0;
135 		m->version = 0;
136 		pos = m->index;
137 		p = m->op->start(m, &pos);
138 	}
139 	m->op->stop(m, p);
140 	m->count = 0;
141 	goto Done;
142 Fill:
143 	/* they want more? let's try to get some more */
144 	while (m->count < size) {
145 		size_t offs = m->count;
146 		loff_t next = pos;
147 		p = m->op->next(m, p, &next);
148 		if (!p || IS_ERR(p)) {
149 			err = PTR_ERR(p);
150 			break;
151 		}
152 		err = m->op->show(m, p);
153 		if (m->count == m->size || err) {
154 			m->count = offs;
155 			if (likely(err <= 0))
156 				break;
157 		}
158 		pos = next;
159 	}
160 	m->op->stop(m, p);
161 	n = min(m->count, size);
162 	err = copy_to_user(buf, m->buf, n);
163 	if (err)
164 		goto Efault;
165 	copied += n;
166 	m->count -= n;
167 	if (m->count)
168 		m->from = n;
169 	else
170 		pos++;
171 	m->index = pos;
172 Done:
173 	if (!copied)
174 		copied = err;
175 	else
176 		*ppos += copied;
177 	file->f_version = m->version;
178 	mutex_unlock(&m->lock);
179 	return copied;
180 Enomem:
181 	err = -ENOMEM;
182 	goto Done;
183 Efault:
184 	err = -EFAULT;
185 	goto Done;
186 }
187 EXPORT_SYMBOL(seq_read);
188 
189 static int traverse(struct seq_file *m, loff_t offset)
190 {
191 	loff_t pos = 0, index;
192 	int error = 0;
193 	void *p;
194 
195 	m->version = 0;
196 	index = 0;
197 	m->count = m->from = 0;
198 	if (!offset) {
199 		m->index = index;
200 		return 0;
201 	}
202 	if (!m->buf) {
203 		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
204 		if (!m->buf)
205 			return -ENOMEM;
206 	}
207 	p = m->op->start(m, &index);
208 	while (p) {
209 		error = PTR_ERR(p);
210 		if (IS_ERR(p))
211 			break;
212 		error = m->op->show(m, p);
213 		if (error < 0)
214 			break;
215 		if (unlikely(error)) {
216 			error = 0;
217 			m->count = 0;
218 		}
219 		if (m->count == m->size)
220 			goto Eoverflow;
221 		if (pos + m->count > offset) {
222 			m->from = offset - pos;
223 			m->count -= m->from;
224 			m->index = index;
225 			break;
226 		}
227 		pos += m->count;
228 		m->count = 0;
229 		if (pos == offset) {
230 			index++;
231 			m->index = index;
232 			break;
233 		}
234 		p = m->op->next(m, p, &index);
235 	}
236 	m->op->stop(m, p);
237 	return error;
238 
239 Eoverflow:
240 	m->op->stop(m, p);
241 	kfree(m->buf);
242 	m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
243 	return !m->buf ? -ENOMEM : -EAGAIN;
244 }
245 
246 /**
247  *	seq_lseek -	->llseek() method for sequential files.
248  *	@file: the file in question
249  *	@offset: new position
250  *	@origin: 0 for absolute, 1 for relative position
251  *
252  *	Ready-made ->f_op->llseek()
253  */
254 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
255 {
256 	struct seq_file *m = (struct seq_file *)file->private_data;
257 	loff_t retval = -EINVAL;
258 
259 	mutex_lock(&m->lock);
260 	m->version = file->f_version;
261 	switch (origin) {
262 		case 1:
263 			offset += file->f_pos;
264 		case 0:
265 			if (offset < 0)
266 				break;
267 			retval = offset;
268 			if (offset != file->f_pos) {
269 				while ((retval=traverse(m, offset)) == -EAGAIN)
270 					;
271 				if (retval) {
272 					/* with extreme prejudice... */
273 					file->f_pos = 0;
274 					m->version = 0;
275 					m->index = 0;
276 					m->count = 0;
277 				} else {
278 					retval = file->f_pos = offset;
279 				}
280 			}
281 	}
282 	file->f_version = m->version;
283 	mutex_unlock(&m->lock);
284 	return retval;
285 }
286 EXPORT_SYMBOL(seq_lseek);
287 
288 /**
289  *	seq_release -	free the structures associated with sequential file.
290  *	@file: file in question
291  *	@inode: file->f_path.dentry->d_inode
292  *
293  *	Frees the structures associated with sequential file; can be used
294  *	as ->f_op->release() if you don't have private data to destroy.
295  */
296 int seq_release(struct inode *inode, struct file *file)
297 {
298 	struct seq_file *m = (struct seq_file *)file->private_data;
299 	kfree(m->buf);
300 	kfree(m);
301 	return 0;
302 }
303 EXPORT_SYMBOL(seq_release);
304 
305 /**
306  *	seq_escape -	print string into buffer, escaping some characters
307  *	@m:	target buffer
308  *	@s:	string
309  *	@esc:	set of characters that need escaping
310  *
311  *	Puts string into buffer, replacing each occurrence of character from
312  *	@esc with usual octal escape.  Returns 0 in case of success, -1 - in
313  *	case of overflow.
314  */
315 int seq_escape(struct seq_file *m, const char *s, const char *esc)
316 {
317 	char *end = m->buf + m->size;
318         char *p;
319 	char c;
320 
321         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
322 		if (!strchr(esc, c)) {
323 			*p++ = c;
324 			continue;
325 		}
326 		if (p + 3 < end) {
327 			*p++ = '\\';
328 			*p++ = '0' + ((c & 0300) >> 6);
329 			*p++ = '0' + ((c & 070) >> 3);
330 			*p++ = '0' + (c & 07);
331 			continue;
332 		}
333 		m->count = m->size;
334 		return -1;
335         }
336 	m->count = p - m->buf;
337         return 0;
338 }
339 EXPORT_SYMBOL(seq_escape);
340 
341 int seq_printf(struct seq_file *m, const char *f, ...)
342 {
343 	va_list args;
344 	int len;
345 
346 	if (m->count < m->size) {
347 		va_start(args, f);
348 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
349 		va_end(args);
350 		if (m->count + len < m->size) {
351 			m->count += len;
352 			return 0;
353 		}
354 	}
355 	m->count = m->size;
356 	return -1;
357 }
358 EXPORT_SYMBOL(seq_printf);
359 
360 static char *mangle_path(char *s, char *p, char *esc)
361 {
362 	while (s <= p) {
363 		char c = *p++;
364 		if (!c) {
365 			return s;
366 		} else if (!strchr(esc, c)) {
367 			*s++ = c;
368 		} else if (s + 4 > p) {
369 			break;
370 		} else {
371 			*s++ = '\\';
372 			*s++ = '0' + ((c & 0300) >> 6);
373 			*s++ = '0' + ((c & 070) >> 3);
374 			*s++ = '0' + (c & 07);
375 		}
376 	}
377 	return NULL;
378 }
379 
380 /*
381  * return the absolute path of 'dentry' residing in mount 'mnt'.
382  */
383 int seq_path(struct seq_file *m, struct path *path, char *esc)
384 {
385 	if (m->count < m->size) {
386 		char *s = m->buf + m->count;
387 		char *p = d_path(path, s, m->size - m->count);
388 		if (!IS_ERR(p)) {
389 			s = mangle_path(s, p, esc);
390 			if (s) {
391 				p = m->buf + m->count;
392 				m->count = s - m->buf;
393 				return s - p;
394 			}
395 		}
396 	}
397 	m->count = m->size;
398 	return -1;
399 }
400 EXPORT_SYMBOL(seq_path);
401 
402 /*
403  * Same as seq_path, but relative to supplied root.
404  *
405  * root may be changed, see __d_path().
406  */
407 int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
408 		  char *esc)
409 {
410 	int err = -ENAMETOOLONG;
411 	if (m->count < m->size) {
412 		char *s = m->buf + m->count;
413 		char *p;
414 
415 		spin_lock(&dcache_lock);
416 		p = __d_path(path, root, s, m->size - m->count);
417 		spin_unlock(&dcache_lock);
418 		err = PTR_ERR(p);
419 		if (!IS_ERR(p)) {
420 			s = mangle_path(s, p, esc);
421 			if (s) {
422 				p = m->buf + m->count;
423 				m->count = s - m->buf;
424 				return 0;
425 			}
426 		}
427 	}
428 	m->count = m->size;
429 	return err;
430 }
431 
432 /*
433  * returns the path of the 'dentry' from the root of its filesystem.
434  */
435 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
436 {
437 	if (m->count < m->size) {
438 		char *s = m->buf + m->count;
439 		char *p = dentry_path(dentry, s, m->size - m->count);
440 		if (!IS_ERR(p)) {
441 			s = mangle_path(s, p, esc);
442 			if (s) {
443 				p = m->buf + m->count;
444 				m->count = s - m->buf;
445 				return s - p;
446 			}
447 		}
448 	}
449 	m->count = m->size;
450 	return -1;
451 }
452 
453 int seq_bitmap(struct seq_file *m, unsigned long *bits, unsigned int nr_bits)
454 {
455 	size_t len = bitmap_scnprintf_len(nr_bits);
456 
457 	if (m->count + len < m->size) {
458 		bitmap_scnprintf(m->buf + m->count, m->size - m->count,
459 				 bits, nr_bits);
460 		m->count += len;
461 		return 0;
462 	}
463 	m->count = m->size;
464 	return -1;
465 }
466 
467 static void *single_start(struct seq_file *p, loff_t *pos)
468 {
469 	return NULL + (*pos == 0);
470 }
471 
472 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
473 {
474 	++*pos;
475 	return NULL;
476 }
477 
478 static void single_stop(struct seq_file *p, void *v)
479 {
480 }
481 
482 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
483 		void *data)
484 {
485 	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
486 	int res = -ENOMEM;
487 
488 	if (op) {
489 		op->start = single_start;
490 		op->next = single_next;
491 		op->stop = single_stop;
492 		op->show = show;
493 		res = seq_open(file, op);
494 		if (!res)
495 			((struct seq_file *)file->private_data)->private = data;
496 		else
497 			kfree(op);
498 	}
499 	return res;
500 }
501 EXPORT_SYMBOL(single_open);
502 
503 int single_release(struct inode *inode, struct file *file)
504 {
505 	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
506 	int res = seq_release(inode, file);
507 	kfree(op);
508 	return res;
509 }
510 EXPORT_SYMBOL(single_release);
511 
512 int seq_release_private(struct inode *inode, struct file *file)
513 {
514 	struct seq_file *seq = file->private_data;
515 
516 	kfree(seq->private);
517 	seq->private = NULL;
518 	return seq_release(inode, file);
519 }
520 EXPORT_SYMBOL(seq_release_private);
521 
522 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
523 		int psize)
524 {
525 	int rc;
526 	void *private;
527 	struct seq_file *seq;
528 
529 	private = kzalloc(psize, GFP_KERNEL);
530 	if (private == NULL)
531 		goto out;
532 
533 	rc = seq_open(f, ops);
534 	if (rc < 0)
535 		goto out_free;
536 
537 	seq = f->private_data;
538 	seq->private = private;
539 	return private;
540 
541 out_free:
542 	kfree(private);
543 out:
544 	return NULL;
545 }
546 EXPORT_SYMBOL(__seq_open_private);
547 
548 int seq_open_private(struct file *filp, const struct seq_operations *ops,
549 		int psize)
550 {
551 	return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
552 }
553 EXPORT_SYMBOL(seq_open_private);
554 
555 int seq_putc(struct seq_file *m, char c)
556 {
557 	if (m->count < m->size) {
558 		m->buf[m->count++] = c;
559 		return 0;
560 	}
561 	return -1;
562 }
563 EXPORT_SYMBOL(seq_putc);
564 
565 int seq_puts(struct seq_file *m, const char *s)
566 {
567 	int len = strlen(s);
568 	if (m->count + len < m->size) {
569 		memcpy(m->buf + m->count, s, len);
570 		m->count += len;
571 		return 0;
572 	}
573 	m->count = m->size;
574 	return -1;
575 }
576 EXPORT_SYMBOL(seq_puts);
577 
578 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
579 {
580 	struct list_head *lh;
581 
582 	list_for_each(lh, head)
583 		if (pos-- == 0)
584 			return lh;
585 
586 	return NULL;
587 }
588 
589 EXPORT_SYMBOL(seq_list_start);
590 
591 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
592 {
593 	if (!pos)
594 		return head;
595 
596 	return seq_list_start(head, pos - 1);
597 }
598 
599 EXPORT_SYMBOL(seq_list_start_head);
600 
601 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
602 {
603 	struct list_head *lh;
604 
605 	lh = ((struct list_head *)v)->next;
606 	++*ppos;
607 	return lh == head ? NULL : lh;
608 }
609 
610 EXPORT_SYMBOL(seq_list_next);
611