xref: /openbmc/linux/fs/seq_file.c (revision 22246614) 
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 	while (1) {
112 		pos = m->index;
113 		p = m->op->start(m, &pos);
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 (m->count < m->size)
123 			goto Fill;
124 		m->op->stop(m, p);
125 		kfree(m->buf);
126 		m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
127 		if (!m->buf)
128 			goto Enomem;
129 		m->count = 0;
130 		m->version = 0;
131 	}
132 	m->op->stop(m, p);
133 	m->count = 0;
134 	goto Done;
135 Fill:
136 	/* they want more? let's try to get some more */
137 	while (m->count < size) {
138 		size_t offs = m->count;
139 		loff_t next = pos;
140 		p = m->op->next(m, p, &next);
141 		if (!p || IS_ERR(p)) {
142 			err = PTR_ERR(p);
143 			break;
144 		}
145 		err = m->op->show(m, p);
146 		if (m->count == m->size || err) {
147 			m->count = offs;
148 			if (likely(err <= 0))
149 				break;
150 		}
151 		pos = next;
152 	}
153 	m->op->stop(m, p);
154 	n = min(m->count, size);
155 	err = copy_to_user(buf, m->buf, n);
156 	if (err)
157 		goto Efault;
158 	copied += n;
159 	m->count -= n;
160 	if (m->count)
161 		m->from = n;
162 	else
163 		pos++;
164 	m->index = pos;
165 Done:
166 	if (!copied)
167 		copied = err;
168 	else
169 		*ppos += copied;
170 	file->f_version = m->version;
171 	mutex_unlock(&m->lock);
172 	return copied;
173 Enomem:
174 	err = -ENOMEM;
175 	goto Done;
176 Efault:
177 	err = -EFAULT;
178 	goto Done;
179 }
180 EXPORT_SYMBOL(seq_read);
181 
182 static int traverse(struct seq_file *m, loff_t offset)
183 {
184 	loff_t pos = 0, index;
185 	int error = 0;
186 	void *p;
187 
188 	m->version = 0;
189 	index = 0;
190 	m->count = m->from = 0;
191 	if (!offset) {
192 		m->index = index;
193 		return 0;
194 	}
195 	if (!m->buf) {
196 		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
197 		if (!m->buf)
198 			return -ENOMEM;
199 	}
200 	p = m->op->start(m, &index);
201 	while (p) {
202 		error = PTR_ERR(p);
203 		if (IS_ERR(p))
204 			break;
205 		error = m->op->show(m, p);
206 		if (error < 0)
207 			break;
208 		if (unlikely(error)) {
209 			error = 0;
210 			m->count = 0;
211 		}
212 		if (m->count == m->size)
213 			goto Eoverflow;
214 		if (pos + m->count > offset) {
215 			m->from = offset - pos;
216 			m->count -= m->from;
217 			m->index = index;
218 			break;
219 		}
220 		pos += m->count;
221 		m->count = 0;
222 		if (pos == offset) {
223 			index++;
224 			m->index = index;
225 			break;
226 		}
227 		p = m->op->next(m, p, &index);
228 	}
229 	m->op->stop(m, p);
230 	return error;
231 
232 Eoverflow:
233 	m->op->stop(m, p);
234 	kfree(m->buf);
235 	m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
236 	return !m->buf ? -ENOMEM : -EAGAIN;
237 }
238 
239 /**
240  *	seq_lseek -	->llseek() method for sequential files.
241  *	@file: the file in question
242  *	@offset: new position
243  *	@origin: 0 for absolute, 1 for relative position
244  *
245  *	Ready-made ->f_op->llseek()
246  */
247 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
248 {
249 	struct seq_file *m = (struct seq_file *)file->private_data;
250 	loff_t retval = -EINVAL;
251 
252 	mutex_lock(&m->lock);
253 	m->version = file->f_version;
254 	switch (origin) {
255 		case 1:
256 			offset += file->f_pos;
257 		case 0:
258 			if (offset < 0)
259 				break;
260 			retval = offset;
261 			if (offset != file->f_pos) {
262 				while ((retval=traverse(m, offset)) == -EAGAIN)
263 					;
264 				if (retval) {
265 					/* with extreme prejudice... */
266 					file->f_pos = 0;
267 					m->version = 0;
268 					m->index = 0;
269 					m->count = 0;
270 				} else {
271 					retval = file->f_pos = offset;
272 				}
273 			}
274 	}
275 	file->f_version = m->version;
276 	mutex_unlock(&m->lock);
277 	return retval;
278 }
279 EXPORT_SYMBOL(seq_lseek);
280 
281 /**
282  *	seq_release -	free the structures associated with sequential file.
283  *	@file: file in question
284  *	@inode: file->f_path.dentry->d_inode
285  *
286  *	Frees the structures associated with sequential file; can be used
287  *	as ->f_op->release() if you don't have private data to destroy.
288  */
289 int seq_release(struct inode *inode, struct file *file)
290 {
291 	struct seq_file *m = (struct seq_file *)file->private_data;
292 	kfree(m->buf);
293 	kfree(m);
294 	return 0;
295 }
296 EXPORT_SYMBOL(seq_release);
297 
298 /**
299  *	seq_escape -	print string into buffer, escaping some characters
300  *	@m:	target buffer
301  *	@s:	string
302  *	@esc:	set of characters that need escaping
303  *
304  *	Puts string into buffer, replacing each occurrence of character from
305  *	@esc with usual octal escape.  Returns 0 in case of success, -1 - in
306  *	case of overflow.
307  */
308 int seq_escape(struct seq_file *m, const char *s, const char *esc)
309 {
310 	char *end = m->buf + m->size;
311         char *p;
312 	char c;
313 
314         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
315 		if (!strchr(esc, c)) {
316 			*p++ = c;
317 			continue;
318 		}
319 		if (p + 3 < end) {
320 			*p++ = '\\';
321 			*p++ = '0' + ((c & 0300) >> 6);
322 			*p++ = '0' + ((c & 070) >> 3);
323 			*p++ = '0' + (c & 07);
324 			continue;
325 		}
326 		m->count = m->size;
327 		return -1;
328         }
329 	m->count = p - m->buf;
330         return 0;
331 }
332 EXPORT_SYMBOL(seq_escape);
333 
334 int seq_printf(struct seq_file *m, const char *f, ...)
335 {
336 	va_list args;
337 	int len;
338 
339 	if (m->count < m->size) {
340 		va_start(args, f);
341 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
342 		va_end(args);
343 		if (m->count + len < m->size) {
344 			m->count += len;
345 			return 0;
346 		}
347 	}
348 	m->count = m->size;
349 	return -1;
350 }
351 EXPORT_SYMBOL(seq_printf);
352 
353 static char *mangle_path(char *s, char *p, char *esc)
354 {
355 	while (s <= p) {
356 		char c = *p++;
357 		if (!c) {
358 			return s;
359 		} else if (!strchr(esc, c)) {
360 			*s++ = c;
361 		} else if (s + 4 > p) {
362 			break;
363 		} else {
364 			*s++ = '\\';
365 			*s++ = '0' + ((c & 0300) >> 6);
366 			*s++ = '0' + ((c & 070) >> 3);
367 			*s++ = '0' + (c & 07);
368 		}
369 	}
370 	return NULL;
371 }
372 
373 /*
374  * return the absolute path of 'dentry' residing in mount 'mnt'.
375  */
376 int seq_path(struct seq_file *m, struct path *path, char *esc)
377 {
378 	if (m->count < m->size) {
379 		char *s = m->buf + m->count;
380 		char *p = d_path(path, s, m->size - m->count);
381 		if (!IS_ERR(p)) {
382 			s = mangle_path(s, p, esc);
383 			if (s) {
384 				p = m->buf + m->count;
385 				m->count = s - m->buf;
386 				return s - p;
387 			}
388 		}
389 	}
390 	m->count = m->size;
391 	return -1;
392 }
393 EXPORT_SYMBOL(seq_path);
394 
395 /*
396  * Same as seq_path, but relative to supplied root.
397  *
398  * root may be changed, see __d_path().
399  */
400 int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
401 		  char *esc)
402 {
403 	int err = -ENAMETOOLONG;
404 	if (m->count < m->size) {
405 		char *s = m->buf + m->count;
406 		char *p;
407 
408 		spin_lock(&dcache_lock);
409 		p = __d_path(path, root, s, m->size - m->count);
410 		spin_unlock(&dcache_lock);
411 		err = PTR_ERR(p);
412 		if (!IS_ERR(p)) {
413 			s = mangle_path(s, p, esc);
414 			if (s) {
415 				p = m->buf + m->count;
416 				m->count = s - m->buf;
417 				return 0;
418 			}
419 		}
420 	}
421 	m->count = m->size;
422 	return err;
423 }
424 
425 /*
426  * returns the path of the 'dentry' from the root of its filesystem.
427  */
428 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
429 {
430 	if (m->count < m->size) {
431 		char *s = m->buf + m->count;
432 		char *p = dentry_path(dentry, s, m->size - m->count);
433 		if (!IS_ERR(p)) {
434 			s = mangle_path(s, p, esc);
435 			if (s) {
436 				p = m->buf + m->count;
437 				m->count = s - m->buf;
438 				return s - p;
439 			}
440 		}
441 	}
442 	m->count = m->size;
443 	return -1;
444 }
445 
446 static void *single_start(struct seq_file *p, loff_t *pos)
447 {
448 	return NULL + (*pos == 0);
449 }
450 
451 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
452 {
453 	++*pos;
454 	return NULL;
455 }
456 
457 static void single_stop(struct seq_file *p, void *v)
458 {
459 }
460 
461 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
462 		void *data)
463 {
464 	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
465 	int res = -ENOMEM;
466 
467 	if (op) {
468 		op->start = single_start;
469 		op->next = single_next;
470 		op->stop = single_stop;
471 		op->show = show;
472 		res = seq_open(file, op);
473 		if (!res)
474 			((struct seq_file *)file->private_data)->private = data;
475 		else
476 			kfree(op);
477 	}
478 	return res;
479 }
480 EXPORT_SYMBOL(single_open);
481 
482 int single_release(struct inode *inode, struct file *file)
483 {
484 	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
485 	int res = seq_release(inode, file);
486 	kfree(op);
487 	return res;
488 }
489 EXPORT_SYMBOL(single_release);
490 
491 int seq_release_private(struct inode *inode, struct file *file)
492 {
493 	struct seq_file *seq = file->private_data;
494 
495 	kfree(seq->private);
496 	seq->private = NULL;
497 	return seq_release(inode, file);
498 }
499 EXPORT_SYMBOL(seq_release_private);
500 
501 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
502 		int psize)
503 {
504 	int rc;
505 	void *private;
506 	struct seq_file *seq;
507 
508 	private = kzalloc(psize, GFP_KERNEL);
509 	if (private == NULL)
510 		goto out;
511 
512 	rc = seq_open(f, ops);
513 	if (rc < 0)
514 		goto out_free;
515 
516 	seq = f->private_data;
517 	seq->private = private;
518 	return private;
519 
520 out_free:
521 	kfree(private);
522 out:
523 	return NULL;
524 }
525 EXPORT_SYMBOL(__seq_open_private);
526 
527 int seq_open_private(struct file *filp, const struct seq_operations *ops,
528 		int psize)
529 {
530 	return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
531 }
532 EXPORT_SYMBOL(seq_open_private);
533 
534 int seq_putc(struct seq_file *m, char c)
535 {
536 	if (m->count < m->size) {
537 		m->buf[m->count++] = c;
538 		return 0;
539 	}
540 	return -1;
541 }
542 EXPORT_SYMBOL(seq_putc);
543 
544 int seq_puts(struct seq_file *m, const char *s)
545 {
546 	int len = strlen(s);
547 	if (m->count + len < m->size) {
548 		memcpy(m->buf + m->count, s, len);
549 		m->count += len;
550 		return 0;
551 	}
552 	m->count = m->size;
553 	return -1;
554 }
555 EXPORT_SYMBOL(seq_puts);
556 
557 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
558 {
559 	struct list_head *lh;
560 
561 	list_for_each(lh, head)
562 		if (pos-- == 0)
563 			return lh;
564 
565 	return NULL;
566 }
567 
568 EXPORT_SYMBOL(seq_list_start);
569 
570 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
571 {
572 	if (!pos)
573 		return head;
574 
575 	return seq_list_start(head, pos - 1);
576 }
577 
578 EXPORT_SYMBOL(seq_list_start_head);
579 
580 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
581 {
582 	struct list_head *lh;
583 
584 	lh = ((struct list_head *)v)->next;
585 	++*ppos;
586 	return lh == head ? NULL : lh;
587 }
588 
589 EXPORT_SYMBOL(seq_list_next);
590