xref: /openbmc/linux/fs/seq_file.c (revision 9b9c2cd4)
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/export.h>
10 #include <linux/seq_file.h>
11 #include <linux/vmalloc.h>
12 #include <linux/slab.h>
13 #include <linux/cred.h>
14 #include <linux/mm.h>
15 #include <linux/printk.h>
16 #include <linux/string_helpers.h>
17 
18 #include <asm/uaccess.h>
19 #include <asm/page.h>
20 
21 static void seq_set_overflow(struct seq_file *m)
22 {
23 	m->count = m->size;
24 }
25 
26 static void *seq_buf_alloc(unsigned long size)
27 {
28 	void *buf;
29 	gfp_t gfp = GFP_KERNEL;
30 
31 	/*
32 	 * For high order allocations, use __GFP_NORETRY to avoid oom-killing -
33 	 * it's better to fall back to vmalloc() than to kill things.  For small
34 	 * allocations, just use GFP_KERNEL which will oom kill, thus no need
35 	 * for vmalloc fallback.
36 	 */
37 	if (size > PAGE_SIZE)
38 		gfp |= __GFP_NORETRY | __GFP_NOWARN;
39 	buf = kmalloc(size, gfp);
40 	if (!buf && size > PAGE_SIZE)
41 		buf = vmalloc(size);
42 	return buf;
43 }
44 
45 /**
46  *	seq_open -	initialize sequential file
47  *	@file: file we initialize
48  *	@op: method table describing the sequence
49  *
50  *	seq_open() sets @file, associating it with a sequence described
51  *	by @op.  @op->start() sets the iterator up and returns the first
52  *	element of sequence. @op->stop() shuts it down.  @op->next()
53  *	returns the next element of sequence.  @op->show() prints element
54  *	into the buffer.  In case of error ->start() and ->next() return
55  *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
56  *	returns 0 in case of success and negative number in case of error.
57  *	Returning SEQ_SKIP means "discard this element and move on".
58  *	Note: seq_open() will allocate a struct seq_file and store its
59  *	pointer in @file->private_data. This pointer should not be modified.
60  */
61 int seq_open(struct file *file, const struct seq_operations *op)
62 {
63 	struct seq_file *p;
64 
65 	WARN_ON(file->private_data);
66 
67 	p = kzalloc(sizeof(*p), GFP_KERNEL);
68 	if (!p)
69 		return -ENOMEM;
70 
71 	file->private_data = p;
72 
73 	mutex_init(&p->lock);
74 	p->op = op;
75 #ifdef CONFIG_USER_NS
76 	p->user_ns = file->f_cred->user_ns;
77 #endif
78 
79 	/*
80 	 * Wrappers around seq_open(e.g. swaps_open) need to be
81 	 * aware of this. If they set f_version themselves, they
82 	 * should call seq_open first and then set f_version.
83 	 */
84 	file->f_version = 0;
85 
86 	/*
87 	 * seq_files support lseek() and pread().  They do not implement
88 	 * write() at all, but we clear FMODE_PWRITE here for historical
89 	 * reasons.
90 	 *
91 	 * If a client of seq_files a) implements file.write() and b) wishes to
92 	 * support pwrite() then that client will need to implement its own
93 	 * file.open() which calls seq_open() and then sets FMODE_PWRITE.
94 	 */
95 	file->f_mode &= ~FMODE_PWRITE;
96 	return 0;
97 }
98 EXPORT_SYMBOL(seq_open);
99 
100 static int traverse(struct seq_file *m, loff_t offset)
101 {
102 	loff_t pos = 0, index;
103 	int error = 0;
104 	void *p;
105 
106 	m->version = 0;
107 	index = 0;
108 	m->count = m->from = 0;
109 	if (!offset) {
110 		m->index = index;
111 		return 0;
112 	}
113 	if (!m->buf) {
114 		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
115 		if (!m->buf)
116 			return -ENOMEM;
117 	}
118 	p = m->op->start(m, &index);
119 	while (p) {
120 		error = PTR_ERR(p);
121 		if (IS_ERR(p))
122 			break;
123 		error = m->op->show(m, p);
124 		if (error < 0)
125 			break;
126 		if (unlikely(error)) {
127 			error = 0;
128 			m->count = 0;
129 		}
130 		if (seq_has_overflowed(m))
131 			goto Eoverflow;
132 		if (pos + m->count > offset) {
133 			m->from = offset - pos;
134 			m->count -= m->from;
135 			m->index = index;
136 			break;
137 		}
138 		pos += m->count;
139 		m->count = 0;
140 		if (pos == offset) {
141 			index++;
142 			m->index = index;
143 			break;
144 		}
145 		p = m->op->next(m, p, &index);
146 	}
147 	m->op->stop(m, p);
148 	m->index = index;
149 	return error;
150 
151 Eoverflow:
152 	m->op->stop(m, p);
153 	kvfree(m->buf);
154 	m->count = 0;
155 	m->buf = seq_buf_alloc(m->size <<= 1);
156 	return !m->buf ? -ENOMEM : -EAGAIN;
157 }
158 
159 /**
160  *	seq_read -	->read() method for sequential files.
161  *	@file: the file to read from
162  *	@buf: the buffer to read to
163  *	@size: the maximum number of bytes to read
164  *	@ppos: the current position in the file
165  *
166  *	Ready-made ->f_op->read()
167  */
168 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
169 {
170 	struct seq_file *m = file->private_data;
171 	size_t copied = 0;
172 	loff_t pos;
173 	size_t n;
174 	void *p;
175 	int err = 0;
176 
177 	mutex_lock(&m->lock);
178 
179 	/*
180 	 * seq_file->op->..m_start/m_stop/m_next may do special actions
181 	 * or optimisations based on the file->f_version, so we want to
182 	 * pass the file->f_version to those methods.
183 	 *
184 	 * seq_file->version is just copy of f_version, and seq_file
185 	 * methods can treat it simply as file version.
186 	 * It is copied in first and copied out after all operations.
187 	 * It is convenient to have it as  part of structure to avoid the
188 	 * need of passing another argument to all the seq_file methods.
189 	 */
190 	m->version = file->f_version;
191 
192 	/* Don't assume *ppos is where we left it */
193 	if (unlikely(*ppos != m->read_pos)) {
194 		while ((err = traverse(m, *ppos)) == -EAGAIN)
195 			;
196 		if (err) {
197 			/* With prejudice... */
198 			m->read_pos = 0;
199 			m->version = 0;
200 			m->index = 0;
201 			m->count = 0;
202 			goto Done;
203 		} else {
204 			m->read_pos = *ppos;
205 		}
206 	}
207 
208 	/* grab buffer if we didn't have one */
209 	if (!m->buf) {
210 		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
211 		if (!m->buf)
212 			goto Enomem;
213 	}
214 	/* if not empty - flush it first */
215 	if (m->count) {
216 		n = min(m->count, size);
217 		err = copy_to_user(buf, m->buf + m->from, n);
218 		if (err)
219 			goto Efault;
220 		m->count -= n;
221 		m->from += n;
222 		size -= n;
223 		buf += n;
224 		copied += n;
225 		if (!m->count)
226 			m->index++;
227 		if (!size)
228 			goto Done;
229 	}
230 	/* we need at least one record in buffer */
231 	pos = m->index;
232 	p = m->op->start(m, &pos);
233 	while (1) {
234 		err = PTR_ERR(p);
235 		if (!p || IS_ERR(p))
236 			break;
237 		err = m->op->show(m, p);
238 		if (err < 0)
239 			break;
240 		if (unlikely(err))
241 			m->count = 0;
242 		if (unlikely(!m->count)) {
243 			p = m->op->next(m, p, &pos);
244 			m->index = pos;
245 			continue;
246 		}
247 		if (m->count < m->size)
248 			goto Fill;
249 		m->op->stop(m, p);
250 		kvfree(m->buf);
251 		m->count = 0;
252 		m->buf = seq_buf_alloc(m->size <<= 1);
253 		if (!m->buf)
254 			goto Enomem;
255 		m->version = 0;
256 		pos = m->index;
257 		p = m->op->start(m, &pos);
258 	}
259 	m->op->stop(m, p);
260 	m->count = 0;
261 	goto Done;
262 Fill:
263 	/* they want more? let's try to get some more */
264 	while (m->count < size) {
265 		size_t offs = m->count;
266 		loff_t next = pos;
267 		p = m->op->next(m, p, &next);
268 		if (!p || IS_ERR(p)) {
269 			err = PTR_ERR(p);
270 			break;
271 		}
272 		err = m->op->show(m, p);
273 		if (seq_has_overflowed(m) || err) {
274 			m->count = offs;
275 			if (likely(err <= 0))
276 				break;
277 		}
278 		pos = next;
279 	}
280 	m->op->stop(m, p);
281 	n = min(m->count, size);
282 	err = copy_to_user(buf, m->buf, n);
283 	if (err)
284 		goto Efault;
285 	copied += n;
286 	m->count -= n;
287 	if (m->count)
288 		m->from = n;
289 	else
290 		pos++;
291 	m->index = pos;
292 Done:
293 	if (!copied)
294 		copied = err;
295 	else {
296 		*ppos += copied;
297 		m->read_pos += copied;
298 	}
299 	file->f_version = m->version;
300 	mutex_unlock(&m->lock);
301 	return copied;
302 Enomem:
303 	err = -ENOMEM;
304 	goto Done;
305 Efault:
306 	err = -EFAULT;
307 	goto Done;
308 }
309 EXPORT_SYMBOL(seq_read);
310 
311 /**
312  *	seq_lseek -	->llseek() method for sequential files.
313  *	@file: the file in question
314  *	@offset: new position
315  *	@whence: 0 for absolute, 1 for relative position
316  *
317  *	Ready-made ->f_op->llseek()
318  */
319 loff_t seq_lseek(struct file *file, loff_t offset, int whence)
320 {
321 	struct seq_file *m = file->private_data;
322 	loff_t retval = -EINVAL;
323 
324 	mutex_lock(&m->lock);
325 	m->version = file->f_version;
326 	switch (whence) {
327 	case SEEK_CUR:
328 		offset += file->f_pos;
329 	case SEEK_SET:
330 		if (offset < 0)
331 			break;
332 		retval = offset;
333 		if (offset != m->read_pos) {
334 			while ((retval = traverse(m, offset)) == -EAGAIN)
335 				;
336 			if (retval) {
337 				/* with extreme prejudice... */
338 				file->f_pos = 0;
339 				m->read_pos = 0;
340 				m->version = 0;
341 				m->index = 0;
342 				m->count = 0;
343 			} else {
344 				m->read_pos = offset;
345 				retval = file->f_pos = offset;
346 			}
347 		} else {
348 			file->f_pos = offset;
349 		}
350 	}
351 	file->f_version = m->version;
352 	mutex_unlock(&m->lock);
353 	return retval;
354 }
355 EXPORT_SYMBOL(seq_lseek);
356 
357 /**
358  *	seq_release -	free the structures associated with sequential file.
359  *	@file: file in question
360  *	@inode: its inode
361  *
362  *	Frees the structures associated with sequential file; can be used
363  *	as ->f_op->release() if you don't have private data to destroy.
364  */
365 int seq_release(struct inode *inode, struct file *file)
366 {
367 	struct seq_file *m = file->private_data;
368 	kvfree(m->buf);
369 	kfree(m);
370 	return 0;
371 }
372 EXPORT_SYMBOL(seq_release);
373 
374 /**
375  *	seq_escape -	print string into buffer, escaping some characters
376  *	@m:	target buffer
377  *	@s:	string
378  *	@esc:	set of characters that need escaping
379  *
380  *	Puts string into buffer, replacing each occurrence of character from
381  *	@esc with usual octal escape.
382  *	Use seq_has_overflowed() to check for errors.
383  */
384 void seq_escape(struct seq_file *m, const char *s, const char *esc)
385 {
386 	char *buf;
387 	size_t size = seq_get_buf(m, &buf);
388 	int ret;
389 
390 	ret = string_escape_str(s, buf, size, ESCAPE_OCTAL, esc);
391 	seq_commit(m, ret < size ? ret : -1);
392 }
393 EXPORT_SYMBOL(seq_escape);
394 
395 void seq_vprintf(struct seq_file *m, const char *f, va_list args)
396 {
397 	int len;
398 
399 	if (m->count < m->size) {
400 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
401 		if (m->count + len < m->size) {
402 			m->count += len;
403 			return;
404 		}
405 	}
406 	seq_set_overflow(m);
407 }
408 EXPORT_SYMBOL(seq_vprintf);
409 
410 void seq_printf(struct seq_file *m, const char *f, ...)
411 {
412 	va_list args;
413 
414 	va_start(args, f);
415 	seq_vprintf(m, f, args);
416 	va_end(args);
417 }
418 EXPORT_SYMBOL(seq_printf);
419 
420 /**
421  *	mangle_path -	mangle and copy path to buffer beginning
422  *	@s: buffer start
423  *	@p: beginning of path in above buffer
424  *	@esc: set of characters that need escaping
425  *
426  *      Copy the path from @p to @s, replacing each occurrence of character from
427  *      @esc with usual octal escape.
428  *      Returns pointer past last written character in @s, or NULL in case of
429  *      failure.
430  */
431 char *mangle_path(char *s, const char *p, const char *esc)
432 {
433 	while (s <= p) {
434 		char c = *p++;
435 		if (!c) {
436 			return s;
437 		} else if (!strchr(esc, c)) {
438 			*s++ = c;
439 		} else if (s + 4 > p) {
440 			break;
441 		} else {
442 			*s++ = '\\';
443 			*s++ = '0' + ((c & 0300) >> 6);
444 			*s++ = '0' + ((c & 070) >> 3);
445 			*s++ = '0' + (c & 07);
446 		}
447 	}
448 	return NULL;
449 }
450 EXPORT_SYMBOL(mangle_path);
451 
452 /**
453  * seq_path - seq_file interface to print a pathname
454  * @m: the seq_file handle
455  * @path: the struct path to print
456  * @esc: set of characters to escape in the output
457  *
458  * return the absolute path of 'path', as represented by the
459  * dentry / mnt pair in the path parameter.
460  */
461 int seq_path(struct seq_file *m, const struct path *path, const char *esc)
462 {
463 	char *buf;
464 	size_t size = seq_get_buf(m, &buf);
465 	int res = -1;
466 
467 	if (size) {
468 		char *p = d_path(path, buf, size);
469 		if (!IS_ERR(p)) {
470 			char *end = mangle_path(buf, p, esc);
471 			if (end)
472 				res = end - buf;
473 		}
474 	}
475 	seq_commit(m, res);
476 
477 	return res;
478 }
479 EXPORT_SYMBOL(seq_path);
480 
481 /**
482  * seq_file_path - seq_file interface to print a pathname of a file
483  * @m: the seq_file handle
484  * @file: the struct file to print
485  * @esc: set of characters to escape in the output
486  *
487  * return the absolute path to the file.
488  */
489 int seq_file_path(struct seq_file *m, struct file *file, const char *esc)
490 {
491 	return seq_path(m, &file->f_path, esc);
492 }
493 EXPORT_SYMBOL(seq_file_path);
494 
495 /*
496  * Same as seq_path, but relative to supplied root.
497  */
498 int seq_path_root(struct seq_file *m, const struct path *path,
499 		  const struct path *root, const char *esc)
500 {
501 	char *buf;
502 	size_t size = seq_get_buf(m, &buf);
503 	int res = -ENAMETOOLONG;
504 
505 	if (size) {
506 		char *p;
507 
508 		p = __d_path(path, root, buf, size);
509 		if (!p)
510 			return SEQ_SKIP;
511 		res = PTR_ERR(p);
512 		if (!IS_ERR(p)) {
513 			char *end = mangle_path(buf, p, esc);
514 			if (end)
515 				res = end - buf;
516 			else
517 				res = -ENAMETOOLONG;
518 		}
519 	}
520 	seq_commit(m, res);
521 
522 	return res < 0 && res != -ENAMETOOLONG ? res : 0;
523 }
524 
525 /*
526  * returns the path of the 'dentry' from the root of its filesystem.
527  */
528 int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)
529 {
530 	char *buf;
531 	size_t size = seq_get_buf(m, &buf);
532 	int res = -1;
533 
534 	if (size) {
535 		char *p = dentry_path(dentry, buf, size);
536 		if (!IS_ERR(p)) {
537 			char *end = mangle_path(buf, p, esc);
538 			if (end)
539 				res = end - buf;
540 		}
541 	}
542 	seq_commit(m, res);
543 
544 	return res;
545 }
546 EXPORT_SYMBOL(seq_dentry);
547 
548 static void *single_start(struct seq_file *p, loff_t *pos)
549 {
550 	return NULL + (*pos == 0);
551 }
552 
553 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
554 {
555 	++*pos;
556 	return NULL;
557 }
558 
559 static void single_stop(struct seq_file *p, void *v)
560 {
561 }
562 
563 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
564 		void *data)
565 {
566 	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
567 	int res = -ENOMEM;
568 
569 	if (op) {
570 		op->start = single_start;
571 		op->next = single_next;
572 		op->stop = single_stop;
573 		op->show = show;
574 		res = seq_open(file, op);
575 		if (!res)
576 			((struct seq_file *)file->private_data)->private = data;
577 		else
578 			kfree(op);
579 	}
580 	return res;
581 }
582 EXPORT_SYMBOL(single_open);
583 
584 int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
585 		void *data, size_t size)
586 {
587 	char *buf = seq_buf_alloc(size);
588 	int ret;
589 	if (!buf)
590 		return -ENOMEM;
591 	ret = single_open(file, show, data);
592 	if (ret) {
593 		kvfree(buf);
594 		return ret;
595 	}
596 	((struct seq_file *)file->private_data)->buf = buf;
597 	((struct seq_file *)file->private_data)->size = size;
598 	return 0;
599 }
600 EXPORT_SYMBOL(single_open_size);
601 
602 int single_release(struct inode *inode, struct file *file)
603 {
604 	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
605 	int res = seq_release(inode, file);
606 	kfree(op);
607 	return res;
608 }
609 EXPORT_SYMBOL(single_release);
610 
611 int seq_release_private(struct inode *inode, struct file *file)
612 {
613 	struct seq_file *seq = file->private_data;
614 
615 	kfree(seq->private);
616 	seq->private = NULL;
617 	return seq_release(inode, file);
618 }
619 EXPORT_SYMBOL(seq_release_private);
620 
621 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
622 		int psize)
623 {
624 	int rc;
625 	void *private;
626 	struct seq_file *seq;
627 
628 	private = kzalloc(psize, GFP_KERNEL);
629 	if (private == NULL)
630 		goto out;
631 
632 	rc = seq_open(f, ops);
633 	if (rc < 0)
634 		goto out_free;
635 
636 	seq = f->private_data;
637 	seq->private = private;
638 	return private;
639 
640 out_free:
641 	kfree(private);
642 out:
643 	return NULL;
644 }
645 EXPORT_SYMBOL(__seq_open_private);
646 
647 int seq_open_private(struct file *filp, const struct seq_operations *ops,
648 		int psize)
649 {
650 	return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
651 }
652 EXPORT_SYMBOL(seq_open_private);
653 
654 void seq_putc(struct seq_file *m, char c)
655 {
656 	if (m->count >= m->size)
657 		return;
658 
659 	m->buf[m->count++] = c;
660 }
661 EXPORT_SYMBOL(seq_putc);
662 
663 void seq_puts(struct seq_file *m, const char *s)
664 {
665 	int len = strlen(s);
666 
667 	if (m->count + len >= m->size) {
668 		seq_set_overflow(m);
669 		return;
670 	}
671 	memcpy(m->buf + m->count, s, len);
672 	m->count += len;
673 }
674 EXPORT_SYMBOL(seq_puts);
675 
676 /*
677  * A helper routine for putting decimal numbers without rich format of printf().
678  * only 'unsigned long long' is supported.
679  * This routine will put one byte delimiter + number into seq_file.
680  * This routine is very quick when you show lots of numbers.
681  * In usual cases, it will be better to use seq_printf(). It's easier to read.
682  */
683 void seq_put_decimal_ull(struct seq_file *m, char delimiter,
684 			 unsigned long long num)
685 {
686 	int len;
687 
688 	if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
689 		goto overflow;
690 
691 	if (delimiter)
692 		m->buf[m->count++] = delimiter;
693 
694 	if (num < 10) {
695 		m->buf[m->count++] = num + '0';
696 		return;
697 	}
698 
699 	len = num_to_str(m->buf + m->count, m->size - m->count, num);
700 	if (!len)
701 		goto overflow;
702 	m->count += len;
703 	return;
704 
705 overflow:
706 	seq_set_overflow(m);
707 }
708 EXPORT_SYMBOL(seq_put_decimal_ull);
709 
710 void seq_put_decimal_ll(struct seq_file *m, char delimiter, long long num)
711 {
712 	if (num < 0) {
713 		if (m->count + 3 >= m->size) {
714 			seq_set_overflow(m);
715 			return;
716 		}
717 		if (delimiter)
718 			m->buf[m->count++] = delimiter;
719 		num = -num;
720 		delimiter = '-';
721 	}
722 	seq_put_decimal_ull(m, delimiter, num);
723 }
724 EXPORT_SYMBOL(seq_put_decimal_ll);
725 
726 /**
727  * seq_write - write arbitrary data to buffer
728  * @seq: seq_file identifying the buffer to which data should be written
729  * @data: data address
730  * @len: number of bytes
731  *
732  * Return 0 on success, non-zero otherwise.
733  */
734 int seq_write(struct seq_file *seq, const void *data, size_t len)
735 {
736 	if (seq->count + len < seq->size) {
737 		memcpy(seq->buf + seq->count, data, len);
738 		seq->count += len;
739 		return 0;
740 	}
741 	seq_set_overflow(seq);
742 	return -1;
743 }
744 EXPORT_SYMBOL(seq_write);
745 
746 /**
747  * seq_pad - write padding spaces to buffer
748  * @m: seq_file identifying the buffer to which data should be written
749  * @c: the byte to append after padding if non-zero
750  */
751 void seq_pad(struct seq_file *m, char c)
752 {
753 	int size = m->pad_until - m->count;
754 	if (size > 0)
755 		seq_printf(m, "%*s", size, "");
756 	if (c)
757 		seq_putc(m, c);
758 }
759 EXPORT_SYMBOL(seq_pad);
760 
761 /* A complete analogue of print_hex_dump() */
762 void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
763 		  int rowsize, int groupsize, const void *buf, size_t len,
764 		  bool ascii)
765 {
766 	const u8 *ptr = buf;
767 	int i, linelen, remaining = len;
768 	char *buffer;
769 	size_t size;
770 	int ret;
771 
772 	if (rowsize != 16 && rowsize != 32)
773 		rowsize = 16;
774 
775 	for (i = 0; i < len && !seq_has_overflowed(m); i += rowsize) {
776 		linelen = min(remaining, rowsize);
777 		remaining -= rowsize;
778 
779 		switch (prefix_type) {
780 		case DUMP_PREFIX_ADDRESS:
781 			seq_printf(m, "%s%p: ", prefix_str, ptr + i);
782 			break;
783 		case DUMP_PREFIX_OFFSET:
784 			seq_printf(m, "%s%.8x: ", prefix_str, i);
785 			break;
786 		default:
787 			seq_printf(m, "%s", prefix_str);
788 			break;
789 		}
790 
791 		size = seq_get_buf(m, &buffer);
792 		ret = hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
793 					 buffer, size, ascii);
794 		seq_commit(m, ret < size ? ret : -1);
795 
796 		seq_putc(m, '\n');
797 	}
798 }
799 EXPORT_SYMBOL(seq_hex_dump);
800 
801 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
802 {
803 	struct list_head *lh;
804 
805 	list_for_each(lh, head)
806 		if (pos-- == 0)
807 			return lh;
808 
809 	return NULL;
810 }
811 EXPORT_SYMBOL(seq_list_start);
812 
813 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
814 {
815 	if (!pos)
816 		return head;
817 
818 	return seq_list_start(head, pos - 1);
819 }
820 EXPORT_SYMBOL(seq_list_start_head);
821 
822 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
823 {
824 	struct list_head *lh;
825 
826 	lh = ((struct list_head *)v)->next;
827 	++*ppos;
828 	return lh == head ? NULL : lh;
829 }
830 EXPORT_SYMBOL(seq_list_next);
831 
832 /**
833  * seq_hlist_start - start an iteration of a hlist
834  * @head: the head of the hlist
835  * @pos:  the start position of the sequence
836  *
837  * Called at seq_file->op->start().
838  */
839 struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
840 {
841 	struct hlist_node *node;
842 
843 	hlist_for_each(node, head)
844 		if (pos-- == 0)
845 			return node;
846 	return NULL;
847 }
848 EXPORT_SYMBOL(seq_hlist_start);
849 
850 /**
851  * seq_hlist_start_head - start an iteration of a hlist
852  * @head: the head of the hlist
853  * @pos:  the start position of the sequence
854  *
855  * Called at seq_file->op->start(). Call this function if you want to
856  * print a header at the top of the output.
857  */
858 struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
859 {
860 	if (!pos)
861 		return SEQ_START_TOKEN;
862 
863 	return seq_hlist_start(head, pos - 1);
864 }
865 EXPORT_SYMBOL(seq_hlist_start_head);
866 
867 /**
868  * seq_hlist_next - move to the next position of the hlist
869  * @v:    the current iterator
870  * @head: the head of the hlist
871  * @ppos: the current position
872  *
873  * Called at seq_file->op->next().
874  */
875 struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
876 				  loff_t *ppos)
877 {
878 	struct hlist_node *node = v;
879 
880 	++*ppos;
881 	if (v == SEQ_START_TOKEN)
882 		return head->first;
883 	else
884 		return node->next;
885 }
886 EXPORT_SYMBOL(seq_hlist_next);
887 
888 /**
889  * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
890  * @head: the head of the hlist
891  * @pos:  the start position of the sequence
892  *
893  * Called at seq_file->op->start().
894  *
895  * This list-traversal primitive may safely run concurrently with
896  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
897  * as long as the traversal is guarded by rcu_read_lock().
898  */
899 struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
900 				       loff_t pos)
901 {
902 	struct hlist_node *node;
903 
904 	__hlist_for_each_rcu(node, head)
905 		if (pos-- == 0)
906 			return node;
907 	return NULL;
908 }
909 EXPORT_SYMBOL(seq_hlist_start_rcu);
910 
911 /**
912  * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
913  * @head: the head of the hlist
914  * @pos:  the start position of the sequence
915  *
916  * Called at seq_file->op->start(). Call this function if you want to
917  * print a header at the top of the output.
918  *
919  * This list-traversal primitive may safely run concurrently with
920  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
921  * as long as the traversal is guarded by rcu_read_lock().
922  */
923 struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
924 					    loff_t pos)
925 {
926 	if (!pos)
927 		return SEQ_START_TOKEN;
928 
929 	return seq_hlist_start_rcu(head, pos - 1);
930 }
931 EXPORT_SYMBOL(seq_hlist_start_head_rcu);
932 
933 /**
934  * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
935  * @v:    the current iterator
936  * @head: the head of the hlist
937  * @ppos: the current position
938  *
939  * Called at seq_file->op->next().
940  *
941  * This list-traversal primitive may safely run concurrently with
942  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
943  * as long as the traversal is guarded by rcu_read_lock().
944  */
945 struct hlist_node *seq_hlist_next_rcu(void *v,
946 				      struct hlist_head *head,
947 				      loff_t *ppos)
948 {
949 	struct hlist_node *node = v;
950 
951 	++*ppos;
952 	if (v == SEQ_START_TOKEN)
953 		return rcu_dereference(head->first);
954 	else
955 		return rcu_dereference(node->next);
956 }
957 EXPORT_SYMBOL(seq_hlist_next_rcu);
958 
959 /**
960  * seq_hlist_start_precpu - start an iteration of a percpu hlist array
961  * @head: pointer to percpu array of struct hlist_heads
962  * @cpu:  pointer to cpu "cursor"
963  * @pos:  start position of sequence
964  *
965  * Called at seq_file->op->start().
966  */
967 struct hlist_node *
968 seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
969 {
970 	struct hlist_node *node;
971 
972 	for_each_possible_cpu(*cpu) {
973 		hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
974 			if (pos-- == 0)
975 				return node;
976 		}
977 	}
978 	return NULL;
979 }
980 EXPORT_SYMBOL(seq_hlist_start_percpu);
981 
982 /**
983  * seq_hlist_next_percpu - move to the next position of the percpu hlist array
984  * @v:    pointer to current hlist_node
985  * @head: pointer to percpu array of struct hlist_heads
986  * @cpu:  pointer to cpu "cursor"
987  * @pos:  start position of sequence
988  *
989  * Called at seq_file->op->next().
990  */
991 struct hlist_node *
992 seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
993 			int *cpu, loff_t *pos)
994 {
995 	struct hlist_node *node = v;
996 
997 	++*pos;
998 
999 	if (node->next)
1000 		return node->next;
1001 
1002 	for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
1003 	     *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
1004 		struct hlist_head *bucket = per_cpu_ptr(head, *cpu);
1005 
1006 		if (!hlist_empty(bucket))
1007 			return bucket->first;
1008 	}
1009 	return NULL;
1010 }
1011 EXPORT_SYMBOL(seq_hlist_next_percpu);
1012