xref: /openbmc/linux/fs/seq_file.c (revision 8bd1369b)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * linux/fs/seq_file.c
4  *
5  * helper functions for making synthetic files from sequences of records.
6  * initial implementation -- AV, Oct 2001.
7  */
8 
9 #include <linux/cache.h>
10 #include <linux/fs.h>
11 #include <linux/export.h>
12 #include <linux/seq_file.h>
13 #include <linux/vmalloc.h>
14 #include <linux/slab.h>
15 #include <linux/cred.h>
16 #include <linux/mm.h>
17 #include <linux/printk.h>
18 #include <linux/string_helpers.h>
19 
20 #include <linux/uaccess.h>
21 #include <asm/page.h>
22 
23 static struct kmem_cache *seq_file_cache __ro_after_init;
24 
25 static void seq_set_overflow(struct seq_file *m)
26 {
27 	m->count = m->size;
28 }
29 
30 static void *seq_buf_alloc(unsigned long size)
31 {
32 	return kvmalloc(size, GFP_KERNEL_ACCOUNT);
33 }
34 
35 /**
36  *	seq_open -	initialize sequential file
37  *	@file: file we initialize
38  *	@op: method table describing the sequence
39  *
40  *	seq_open() sets @file, associating it with a sequence described
41  *	by @op.  @op->start() sets the iterator up and returns the first
42  *	element of sequence. @op->stop() shuts it down.  @op->next()
43  *	returns the next element of sequence.  @op->show() prints element
44  *	into the buffer.  In case of error ->start() and ->next() return
45  *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
46  *	returns 0 in case of success and negative number in case of error.
47  *	Returning SEQ_SKIP means "discard this element and move on".
48  *	Note: seq_open() will allocate a struct seq_file and store its
49  *	pointer in @file->private_data. This pointer should not be modified.
50  */
51 int seq_open(struct file *file, const struct seq_operations *op)
52 {
53 	struct seq_file *p;
54 
55 	WARN_ON(file->private_data);
56 
57 	p = kmem_cache_zalloc(seq_file_cache, GFP_KERNEL);
58 	if (!p)
59 		return -ENOMEM;
60 
61 	file->private_data = p;
62 
63 	mutex_init(&p->lock);
64 	p->op = op;
65 
66 	// No refcounting: the lifetime of 'p' is constrained
67 	// to the lifetime of the file.
68 	p->file = file;
69 
70 	/*
71 	 * Wrappers around seq_open(e.g. swaps_open) need to be
72 	 * aware of this. If they set f_version themselves, they
73 	 * should call seq_open first and then set f_version.
74 	 */
75 	file->f_version = 0;
76 
77 	/*
78 	 * seq_files support lseek() and pread().  They do not implement
79 	 * write() at all, but we clear FMODE_PWRITE here for historical
80 	 * reasons.
81 	 *
82 	 * If a client of seq_files a) implements file.write() and b) wishes to
83 	 * support pwrite() then that client will need to implement its own
84 	 * file.open() which calls seq_open() and then sets FMODE_PWRITE.
85 	 */
86 	file->f_mode &= ~FMODE_PWRITE;
87 	return 0;
88 }
89 EXPORT_SYMBOL(seq_open);
90 
91 static int traverse(struct seq_file *m, loff_t offset)
92 {
93 	loff_t pos = 0, index;
94 	int error = 0;
95 	void *p;
96 
97 	m->version = 0;
98 	index = 0;
99 	m->count = m->from = 0;
100 	if (!offset) {
101 		m->index = index;
102 		return 0;
103 	}
104 	if (!m->buf) {
105 		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
106 		if (!m->buf)
107 			return -ENOMEM;
108 	}
109 	p = m->op->start(m, &index);
110 	while (p) {
111 		error = PTR_ERR(p);
112 		if (IS_ERR(p))
113 			break;
114 		error = m->op->show(m, p);
115 		if (error < 0)
116 			break;
117 		if (unlikely(error)) {
118 			error = 0;
119 			m->count = 0;
120 		}
121 		if (seq_has_overflowed(m))
122 			goto Eoverflow;
123 		if (pos + m->count > offset) {
124 			m->from = offset - pos;
125 			m->count -= m->from;
126 			m->index = index;
127 			break;
128 		}
129 		pos += m->count;
130 		m->count = 0;
131 		if (pos == offset) {
132 			index++;
133 			m->index = index;
134 			break;
135 		}
136 		p = m->op->next(m, p, &index);
137 	}
138 	m->op->stop(m, p);
139 	m->index = index;
140 	return error;
141 
142 Eoverflow:
143 	m->op->stop(m, p);
144 	kvfree(m->buf);
145 	m->count = 0;
146 	m->buf = seq_buf_alloc(m->size <<= 1);
147 	return !m->buf ? -ENOMEM : -EAGAIN;
148 }
149 
150 /**
151  *	seq_read -	->read() method for sequential files.
152  *	@file: the file to read from
153  *	@buf: the buffer to read to
154  *	@size: the maximum number of bytes to read
155  *	@ppos: the current position in the file
156  *
157  *	Ready-made ->f_op->read()
158  */
159 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
160 {
161 	struct seq_file *m = file->private_data;
162 	size_t copied = 0;
163 	loff_t pos;
164 	size_t n;
165 	void *p;
166 	int err = 0;
167 
168 	mutex_lock(&m->lock);
169 
170 	/*
171 	 * seq_file->op->..m_start/m_stop/m_next may do special actions
172 	 * or optimisations based on the file->f_version, so we want to
173 	 * pass the file->f_version to those methods.
174 	 *
175 	 * seq_file->version is just copy of f_version, and seq_file
176 	 * methods can treat it simply as file version.
177 	 * It is copied in first and copied out after all operations.
178 	 * It is convenient to have it as  part of structure to avoid the
179 	 * need of passing another argument to all the seq_file methods.
180 	 */
181 	m->version = file->f_version;
182 
183 	/*
184 	 * if request is to read from zero offset, reset iterator to first
185 	 * record as it might have been already advanced by previous requests
186 	 */
187 	if (*ppos == 0) {
188 		m->index = 0;
189 		m->version = 0;
190 		m->count = 0;
191 	}
192 
193 	/* Don't assume *ppos is where we left it */
194 	if (unlikely(*ppos != m->read_pos)) {
195 		while ((err = traverse(m, *ppos)) == -EAGAIN)
196 			;
197 		if (err) {
198 			/* With prejudice... */
199 			m->read_pos = 0;
200 			m->version = 0;
201 			m->index = 0;
202 			m->count = 0;
203 			goto Done;
204 		} else {
205 			m->read_pos = *ppos;
206 		}
207 	}
208 
209 	/* grab buffer if we didn't have one */
210 	if (!m->buf) {
211 		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
212 		if (!m->buf)
213 			goto Enomem;
214 	}
215 	/* if not empty - flush it first */
216 	if (m->count) {
217 		n = min(m->count, size);
218 		err = copy_to_user(buf, m->buf + m->from, n);
219 		if (err)
220 			goto Efault;
221 		m->count -= n;
222 		m->from += n;
223 		size -= n;
224 		buf += n;
225 		copied += n;
226 		if (!m->count) {
227 			m->from = 0;
228 			m->index++;
229 		}
230 		if (!size)
231 			goto Done;
232 	}
233 	/* we need at least one record in buffer */
234 	pos = m->index;
235 	p = m->op->start(m, &pos);
236 	while (1) {
237 		err = PTR_ERR(p);
238 		if (!p || IS_ERR(p))
239 			break;
240 		err = m->op->show(m, p);
241 		if (err < 0)
242 			break;
243 		if (unlikely(err))
244 			m->count = 0;
245 		if (unlikely(!m->count)) {
246 			p = m->op->next(m, p, &pos);
247 			m->index = pos;
248 			continue;
249 		}
250 		if (m->count < m->size)
251 			goto Fill;
252 		m->op->stop(m, p);
253 		kvfree(m->buf);
254 		m->count = 0;
255 		m->buf = seq_buf_alloc(m->size <<= 1);
256 		if (!m->buf)
257 			goto Enomem;
258 		m->version = 0;
259 		pos = m->index;
260 		p = m->op->start(m, &pos);
261 	}
262 	m->op->stop(m, p);
263 	m->count = 0;
264 	goto Done;
265 Fill:
266 	/* they want more? let's try to get some more */
267 	while (m->count < size) {
268 		size_t offs = m->count;
269 		loff_t next = pos;
270 		p = m->op->next(m, p, &next);
271 		if (!p || IS_ERR(p)) {
272 			err = PTR_ERR(p);
273 			break;
274 		}
275 		err = m->op->show(m, p);
276 		if (seq_has_overflowed(m) || err) {
277 			m->count = offs;
278 			if (likely(err <= 0))
279 				break;
280 		}
281 		pos = next;
282 	}
283 	m->op->stop(m, p);
284 	n = min(m->count, size);
285 	err = copy_to_user(buf, m->buf, n);
286 	if (err)
287 		goto Efault;
288 	copied += n;
289 	m->count -= n;
290 	if (m->count)
291 		m->from = n;
292 	else
293 		pos++;
294 	m->index = pos;
295 Done:
296 	if (!copied)
297 		copied = err;
298 	else {
299 		*ppos += copied;
300 		m->read_pos += copied;
301 	}
302 	file->f_version = m->version;
303 	mutex_unlock(&m->lock);
304 	return copied;
305 Enomem:
306 	err = -ENOMEM;
307 	goto Done;
308 Efault:
309 	err = -EFAULT;
310 	goto Done;
311 }
312 EXPORT_SYMBOL(seq_read);
313 
314 /**
315  *	seq_lseek -	->llseek() method for sequential files.
316  *	@file: the file in question
317  *	@offset: new position
318  *	@whence: 0 for absolute, 1 for relative position
319  *
320  *	Ready-made ->f_op->llseek()
321  */
322 loff_t seq_lseek(struct file *file, loff_t offset, int whence)
323 {
324 	struct seq_file *m = file->private_data;
325 	loff_t retval = -EINVAL;
326 
327 	mutex_lock(&m->lock);
328 	m->version = file->f_version;
329 	switch (whence) {
330 	case SEEK_CUR:
331 		offset += file->f_pos;
332 	case SEEK_SET:
333 		if (offset < 0)
334 			break;
335 		retval = offset;
336 		if (offset != m->read_pos) {
337 			while ((retval = traverse(m, offset)) == -EAGAIN)
338 				;
339 			if (retval) {
340 				/* with extreme prejudice... */
341 				file->f_pos = 0;
342 				m->read_pos = 0;
343 				m->version = 0;
344 				m->index = 0;
345 				m->count = 0;
346 			} else {
347 				m->read_pos = offset;
348 				retval = file->f_pos = offset;
349 			}
350 		} else {
351 			file->f_pos = offset;
352 		}
353 	}
354 	file->f_version = m->version;
355 	mutex_unlock(&m->lock);
356 	return retval;
357 }
358 EXPORT_SYMBOL(seq_lseek);
359 
360 /**
361  *	seq_release -	free the structures associated with sequential file.
362  *	@file: file in question
363  *	@inode: its inode
364  *
365  *	Frees the structures associated with sequential file; can be used
366  *	as ->f_op->release() if you don't have private data to destroy.
367  */
368 int seq_release(struct inode *inode, struct file *file)
369 {
370 	struct seq_file *m = file->private_data;
371 	kvfree(m->buf);
372 	kmem_cache_free(seq_file_cache, m);
373 	return 0;
374 }
375 EXPORT_SYMBOL(seq_release);
376 
377 /**
378  *	seq_escape -	print string into buffer, escaping some characters
379  *	@m:	target buffer
380  *	@s:	string
381  *	@esc:	set of characters that need escaping
382  *
383  *	Puts string into buffer, replacing each occurrence of character from
384  *	@esc with usual octal escape.
385  *	Use seq_has_overflowed() to check for errors.
386  */
387 void seq_escape(struct seq_file *m, const char *s, const char *esc)
388 {
389 	char *buf;
390 	size_t size = seq_get_buf(m, &buf);
391 	int ret;
392 
393 	ret = string_escape_str(s, buf, size, ESCAPE_OCTAL, esc);
394 	seq_commit(m, ret < size ? ret : -1);
395 }
396 EXPORT_SYMBOL(seq_escape);
397 
398 void seq_vprintf(struct seq_file *m, const char *f, va_list args)
399 {
400 	int len;
401 
402 	if (m->count < m->size) {
403 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
404 		if (m->count + len < m->size) {
405 			m->count += len;
406 			return;
407 		}
408 	}
409 	seq_set_overflow(m);
410 }
411 EXPORT_SYMBOL(seq_vprintf);
412 
413 void seq_printf(struct seq_file *m, const char *f, ...)
414 {
415 	va_list args;
416 
417 	va_start(args, f);
418 	seq_vprintf(m, f, args);
419 	va_end(args);
420 }
421 EXPORT_SYMBOL(seq_printf);
422 
423 /**
424  *	mangle_path -	mangle and copy path to buffer beginning
425  *	@s: buffer start
426  *	@p: beginning of path in above buffer
427  *	@esc: set of characters that need escaping
428  *
429  *      Copy the path from @p to @s, replacing each occurrence of character from
430  *      @esc with usual octal escape.
431  *      Returns pointer past last written character in @s, or NULL in case of
432  *      failure.
433  */
434 char *mangle_path(char *s, const char *p, const char *esc)
435 {
436 	while (s <= p) {
437 		char c = *p++;
438 		if (!c) {
439 			return s;
440 		} else if (!strchr(esc, c)) {
441 			*s++ = c;
442 		} else if (s + 4 > p) {
443 			break;
444 		} else {
445 			*s++ = '\\';
446 			*s++ = '0' + ((c & 0300) >> 6);
447 			*s++ = '0' + ((c & 070) >> 3);
448 			*s++ = '0' + (c & 07);
449 		}
450 	}
451 	return NULL;
452 }
453 EXPORT_SYMBOL(mangle_path);
454 
455 /**
456  * seq_path - seq_file interface to print a pathname
457  * @m: the seq_file handle
458  * @path: the struct path to print
459  * @esc: set of characters to escape in the output
460  *
461  * return the absolute path of 'path', as represented by the
462  * dentry / mnt pair in the path parameter.
463  */
464 int seq_path(struct seq_file *m, const struct path *path, const char *esc)
465 {
466 	char *buf;
467 	size_t size = seq_get_buf(m, &buf);
468 	int res = -1;
469 
470 	if (size) {
471 		char *p = d_path(path, buf, size);
472 		if (!IS_ERR(p)) {
473 			char *end = mangle_path(buf, p, esc);
474 			if (end)
475 				res = end - buf;
476 		}
477 	}
478 	seq_commit(m, res);
479 
480 	return res;
481 }
482 EXPORT_SYMBOL(seq_path);
483 
484 /**
485  * seq_file_path - seq_file interface to print a pathname of a file
486  * @m: the seq_file handle
487  * @file: the struct file to print
488  * @esc: set of characters to escape in the output
489  *
490  * return the absolute path to the file.
491  */
492 int seq_file_path(struct seq_file *m, struct file *file, const char *esc)
493 {
494 	return seq_path(m, &file->f_path, esc);
495 }
496 EXPORT_SYMBOL(seq_file_path);
497 
498 /*
499  * Same as seq_path, but relative to supplied root.
500  */
501 int seq_path_root(struct seq_file *m, const struct path *path,
502 		  const struct path *root, const char *esc)
503 {
504 	char *buf;
505 	size_t size = seq_get_buf(m, &buf);
506 	int res = -ENAMETOOLONG;
507 
508 	if (size) {
509 		char *p;
510 
511 		p = __d_path(path, root, buf, size);
512 		if (!p)
513 			return SEQ_SKIP;
514 		res = PTR_ERR(p);
515 		if (!IS_ERR(p)) {
516 			char *end = mangle_path(buf, p, esc);
517 			if (end)
518 				res = end - buf;
519 			else
520 				res = -ENAMETOOLONG;
521 		}
522 	}
523 	seq_commit(m, res);
524 
525 	return res < 0 && res != -ENAMETOOLONG ? res : 0;
526 }
527 
528 /*
529  * returns the path of the 'dentry' from the root of its filesystem.
530  */
531 int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)
532 {
533 	char *buf;
534 	size_t size = seq_get_buf(m, &buf);
535 	int res = -1;
536 
537 	if (size) {
538 		char *p = dentry_path(dentry, buf, size);
539 		if (!IS_ERR(p)) {
540 			char *end = mangle_path(buf, p, esc);
541 			if (end)
542 				res = end - buf;
543 		}
544 	}
545 	seq_commit(m, res);
546 
547 	return res;
548 }
549 EXPORT_SYMBOL(seq_dentry);
550 
551 static void *single_start(struct seq_file *p, loff_t *pos)
552 {
553 	return NULL + (*pos == 0);
554 }
555 
556 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
557 {
558 	++*pos;
559 	return NULL;
560 }
561 
562 static void single_stop(struct seq_file *p, void *v)
563 {
564 }
565 
566 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
567 		void *data)
568 {
569 	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL_ACCOUNT);
570 	int res = -ENOMEM;
571 
572 	if (op) {
573 		op->start = single_start;
574 		op->next = single_next;
575 		op->stop = single_stop;
576 		op->show = show;
577 		res = seq_open(file, op);
578 		if (!res)
579 			((struct seq_file *)file->private_data)->private = data;
580 		else
581 			kfree(op);
582 	}
583 	return res;
584 }
585 EXPORT_SYMBOL(single_open);
586 
587 int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
588 		void *data, size_t size)
589 {
590 	char *buf = seq_buf_alloc(size);
591 	int ret;
592 	if (!buf)
593 		return -ENOMEM;
594 	ret = single_open(file, show, data);
595 	if (ret) {
596 		kvfree(buf);
597 		return ret;
598 	}
599 	((struct seq_file *)file->private_data)->buf = buf;
600 	((struct seq_file *)file->private_data)->size = size;
601 	return 0;
602 }
603 EXPORT_SYMBOL(single_open_size);
604 
605 int single_release(struct inode *inode, struct file *file)
606 {
607 	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
608 	int res = seq_release(inode, file);
609 	kfree(op);
610 	return res;
611 }
612 EXPORT_SYMBOL(single_release);
613 
614 int seq_release_private(struct inode *inode, struct file *file)
615 {
616 	struct seq_file *seq = file->private_data;
617 
618 	kfree(seq->private);
619 	seq->private = NULL;
620 	return seq_release(inode, file);
621 }
622 EXPORT_SYMBOL(seq_release_private);
623 
624 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
625 		int psize)
626 {
627 	int rc;
628 	void *private;
629 	struct seq_file *seq;
630 
631 	private = kzalloc(psize, GFP_KERNEL_ACCOUNT);
632 	if (private == NULL)
633 		goto out;
634 
635 	rc = seq_open(f, ops);
636 	if (rc < 0)
637 		goto out_free;
638 
639 	seq = f->private_data;
640 	seq->private = private;
641 	return private;
642 
643 out_free:
644 	kfree(private);
645 out:
646 	return NULL;
647 }
648 EXPORT_SYMBOL(__seq_open_private);
649 
650 int seq_open_private(struct file *filp, const struct seq_operations *ops,
651 		int psize)
652 {
653 	return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
654 }
655 EXPORT_SYMBOL(seq_open_private);
656 
657 void seq_putc(struct seq_file *m, char c)
658 {
659 	if (m->count >= m->size)
660 		return;
661 
662 	m->buf[m->count++] = c;
663 }
664 EXPORT_SYMBOL(seq_putc);
665 
666 void seq_puts(struct seq_file *m, const char *s)
667 {
668 	int len = strlen(s);
669 
670 	if (m->count + len >= m->size) {
671 		seq_set_overflow(m);
672 		return;
673 	}
674 	memcpy(m->buf + m->count, s, len);
675 	m->count += len;
676 }
677 EXPORT_SYMBOL(seq_puts);
678 
679 /**
680  * A helper routine for putting decimal numbers without rich format of printf().
681  * only 'unsigned long long' is supported.
682  * @m: seq_file identifying the buffer to which data should be written
683  * @delimiter: a string which is printed before the number
684  * @num: the number
685  * @width: a minimum field width
686  *
687  * This routine will put strlen(delimiter) + number into seq_filed.
688  * This routine is very quick when you show lots of numbers.
689  * In usual cases, it will be better to use seq_printf(). It's easier to read.
690  */
691 void seq_put_decimal_ull_width(struct seq_file *m, const char *delimiter,
692 			 unsigned long long num, unsigned int width)
693 {
694 	int len;
695 
696 	if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
697 		goto overflow;
698 
699 	if (delimiter && delimiter[0]) {
700 		if (delimiter[1] == 0)
701 			seq_putc(m, delimiter[0]);
702 		else
703 			seq_puts(m, delimiter);
704 	}
705 
706 	if (!width)
707 		width = 1;
708 
709 	if (m->count + width >= m->size)
710 		goto overflow;
711 
712 	len = num_to_str(m->buf + m->count, m->size - m->count, num, width);
713 	if (!len)
714 		goto overflow;
715 
716 	m->count += len;
717 	return;
718 
719 overflow:
720 	seq_set_overflow(m);
721 }
722 
723 void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,
724 			 unsigned long long num)
725 {
726 	return seq_put_decimal_ull_width(m, delimiter, num, 0);
727 }
728 EXPORT_SYMBOL(seq_put_decimal_ull);
729 
730 /**
731  * seq_put_hex_ll - put a number in hexadecimal notation
732  * @m: seq_file identifying the buffer to which data should be written
733  * @delimiter: a string which is printed before the number
734  * @v: the number
735  * @width: a minimum field width
736  *
737  * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "%08llx", v)
738  *
739  * This routine is very quick when you show lots of numbers.
740  * In usual cases, it will be better to use seq_printf(). It's easier to read.
741  */
742 void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
743 				unsigned long long v, unsigned int width)
744 {
745 	unsigned int len;
746 	int i;
747 
748 	if (delimiter && delimiter[0]) {
749 		if (delimiter[1] == 0)
750 			seq_putc(m, delimiter[0]);
751 		else
752 			seq_puts(m, delimiter);
753 	}
754 
755 	/* If x is 0, the result of __builtin_clzll is undefined */
756 	if (v == 0)
757 		len = 1;
758 	else
759 		len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
760 
761 	if (len < width)
762 		len = width;
763 
764 	if (m->count + len > m->size) {
765 		seq_set_overflow(m);
766 		return;
767 	}
768 
769 	for (i = len - 1; i >= 0; i--) {
770 		m->buf[m->count + i] = hex_asc[0xf & v];
771 		v = v >> 4;
772 	}
773 	m->count += len;
774 }
775 
776 void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num)
777 {
778 	int len;
779 
780 	if (m->count + 3 >= m->size) /* we'll write 2 bytes at least */
781 		goto overflow;
782 
783 	if (delimiter && delimiter[0]) {
784 		if (delimiter[1] == 0)
785 			seq_putc(m, delimiter[0]);
786 		else
787 			seq_puts(m, delimiter);
788 	}
789 
790 	if (m->count + 2 >= m->size)
791 		goto overflow;
792 
793 	if (num < 0) {
794 		m->buf[m->count++] = '-';
795 		num = -num;
796 	}
797 
798 	if (num < 10) {
799 		m->buf[m->count++] = num + '0';
800 		return;
801 	}
802 
803 	len = num_to_str(m->buf + m->count, m->size - m->count, num, 0);
804 	if (!len)
805 		goto overflow;
806 
807 	m->count += len;
808 	return;
809 
810 overflow:
811 	seq_set_overflow(m);
812 }
813 EXPORT_SYMBOL(seq_put_decimal_ll);
814 
815 /**
816  * seq_write - write arbitrary data to buffer
817  * @seq: seq_file identifying the buffer to which data should be written
818  * @data: data address
819  * @len: number of bytes
820  *
821  * Return 0 on success, non-zero otherwise.
822  */
823 int seq_write(struct seq_file *seq, const void *data, size_t len)
824 {
825 	if (seq->count + len < seq->size) {
826 		memcpy(seq->buf + seq->count, data, len);
827 		seq->count += len;
828 		return 0;
829 	}
830 	seq_set_overflow(seq);
831 	return -1;
832 }
833 EXPORT_SYMBOL(seq_write);
834 
835 /**
836  * seq_pad - write padding spaces to buffer
837  * @m: seq_file identifying the buffer to which data should be written
838  * @c: the byte to append after padding if non-zero
839  */
840 void seq_pad(struct seq_file *m, char c)
841 {
842 	int size = m->pad_until - m->count;
843 	if (size > 0) {
844 		if (size + m->count > m->size) {
845 			seq_set_overflow(m);
846 			return;
847 		}
848 		memset(m->buf + m->count, ' ', size);
849 		m->count += size;
850 	}
851 	if (c)
852 		seq_putc(m, c);
853 }
854 EXPORT_SYMBOL(seq_pad);
855 
856 /* A complete analogue of print_hex_dump() */
857 void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
858 		  int rowsize, int groupsize, const void *buf, size_t len,
859 		  bool ascii)
860 {
861 	const u8 *ptr = buf;
862 	int i, linelen, remaining = len;
863 	char *buffer;
864 	size_t size;
865 	int ret;
866 
867 	if (rowsize != 16 && rowsize != 32)
868 		rowsize = 16;
869 
870 	for (i = 0; i < len && !seq_has_overflowed(m); i += rowsize) {
871 		linelen = min(remaining, rowsize);
872 		remaining -= rowsize;
873 
874 		switch (prefix_type) {
875 		case DUMP_PREFIX_ADDRESS:
876 			seq_printf(m, "%s%p: ", prefix_str, ptr + i);
877 			break;
878 		case DUMP_PREFIX_OFFSET:
879 			seq_printf(m, "%s%.8x: ", prefix_str, i);
880 			break;
881 		default:
882 			seq_printf(m, "%s", prefix_str);
883 			break;
884 		}
885 
886 		size = seq_get_buf(m, &buffer);
887 		ret = hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
888 					 buffer, size, ascii);
889 		seq_commit(m, ret < size ? ret : -1);
890 
891 		seq_putc(m, '\n');
892 	}
893 }
894 EXPORT_SYMBOL(seq_hex_dump);
895 
896 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
897 {
898 	struct list_head *lh;
899 
900 	list_for_each(lh, head)
901 		if (pos-- == 0)
902 			return lh;
903 
904 	return NULL;
905 }
906 EXPORT_SYMBOL(seq_list_start);
907 
908 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
909 {
910 	if (!pos)
911 		return head;
912 
913 	return seq_list_start(head, pos - 1);
914 }
915 EXPORT_SYMBOL(seq_list_start_head);
916 
917 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
918 {
919 	struct list_head *lh;
920 
921 	lh = ((struct list_head *)v)->next;
922 	++*ppos;
923 	return lh == head ? NULL : lh;
924 }
925 EXPORT_SYMBOL(seq_list_next);
926 
927 /**
928  * seq_hlist_start - start an iteration of a hlist
929  * @head: the head of the hlist
930  * @pos:  the start position of the sequence
931  *
932  * Called at seq_file->op->start().
933  */
934 struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
935 {
936 	struct hlist_node *node;
937 
938 	hlist_for_each(node, head)
939 		if (pos-- == 0)
940 			return node;
941 	return NULL;
942 }
943 EXPORT_SYMBOL(seq_hlist_start);
944 
945 /**
946  * seq_hlist_start_head - start an iteration of a hlist
947  * @head: the head of the hlist
948  * @pos:  the start position of the sequence
949  *
950  * Called at seq_file->op->start(). Call this function if you want to
951  * print a header at the top of the output.
952  */
953 struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
954 {
955 	if (!pos)
956 		return SEQ_START_TOKEN;
957 
958 	return seq_hlist_start(head, pos - 1);
959 }
960 EXPORT_SYMBOL(seq_hlist_start_head);
961 
962 /**
963  * seq_hlist_next - move to the next position of the hlist
964  * @v:    the current iterator
965  * @head: the head of the hlist
966  * @ppos: the current position
967  *
968  * Called at seq_file->op->next().
969  */
970 struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
971 				  loff_t *ppos)
972 {
973 	struct hlist_node *node = v;
974 
975 	++*ppos;
976 	if (v == SEQ_START_TOKEN)
977 		return head->first;
978 	else
979 		return node->next;
980 }
981 EXPORT_SYMBOL(seq_hlist_next);
982 
983 /**
984  * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
985  * @head: the head of the hlist
986  * @pos:  the start position of the sequence
987  *
988  * Called at seq_file->op->start().
989  *
990  * This list-traversal primitive may safely run concurrently with
991  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
992  * as long as the traversal is guarded by rcu_read_lock().
993  */
994 struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
995 				       loff_t pos)
996 {
997 	struct hlist_node *node;
998 
999 	__hlist_for_each_rcu(node, head)
1000 		if (pos-- == 0)
1001 			return node;
1002 	return NULL;
1003 }
1004 EXPORT_SYMBOL(seq_hlist_start_rcu);
1005 
1006 /**
1007  * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
1008  * @head: the head of the hlist
1009  * @pos:  the start position of the sequence
1010  *
1011  * Called at seq_file->op->start(). Call this function if you want to
1012  * print a header at the top of the output.
1013  *
1014  * This list-traversal primitive may safely run concurrently with
1015  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
1016  * as long as the traversal is guarded by rcu_read_lock().
1017  */
1018 struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
1019 					    loff_t pos)
1020 {
1021 	if (!pos)
1022 		return SEQ_START_TOKEN;
1023 
1024 	return seq_hlist_start_rcu(head, pos - 1);
1025 }
1026 EXPORT_SYMBOL(seq_hlist_start_head_rcu);
1027 
1028 /**
1029  * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
1030  * @v:    the current iterator
1031  * @head: the head of the hlist
1032  * @ppos: the current position
1033  *
1034  * Called at seq_file->op->next().
1035  *
1036  * This list-traversal primitive may safely run concurrently with
1037  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
1038  * as long as the traversal is guarded by rcu_read_lock().
1039  */
1040 struct hlist_node *seq_hlist_next_rcu(void *v,
1041 				      struct hlist_head *head,
1042 				      loff_t *ppos)
1043 {
1044 	struct hlist_node *node = v;
1045 
1046 	++*ppos;
1047 	if (v == SEQ_START_TOKEN)
1048 		return rcu_dereference(head->first);
1049 	else
1050 		return rcu_dereference(node->next);
1051 }
1052 EXPORT_SYMBOL(seq_hlist_next_rcu);
1053 
1054 /**
1055  * seq_hlist_start_precpu - start an iteration of a percpu hlist array
1056  * @head: pointer to percpu array of struct hlist_heads
1057  * @cpu:  pointer to cpu "cursor"
1058  * @pos:  start position of sequence
1059  *
1060  * Called at seq_file->op->start().
1061  */
1062 struct hlist_node *
1063 seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
1064 {
1065 	struct hlist_node *node;
1066 
1067 	for_each_possible_cpu(*cpu) {
1068 		hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
1069 			if (pos-- == 0)
1070 				return node;
1071 		}
1072 	}
1073 	return NULL;
1074 }
1075 EXPORT_SYMBOL(seq_hlist_start_percpu);
1076 
1077 /**
1078  * seq_hlist_next_percpu - move to the next position of the percpu hlist array
1079  * @v:    pointer to current hlist_node
1080  * @head: pointer to percpu array of struct hlist_heads
1081  * @cpu:  pointer to cpu "cursor"
1082  * @pos:  start position of sequence
1083  *
1084  * Called at seq_file->op->next().
1085  */
1086 struct hlist_node *
1087 seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
1088 			int *cpu, loff_t *pos)
1089 {
1090 	struct hlist_node *node = v;
1091 
1092 	++*pos;
1093 
1094 	if (node->next)
1095 		return node->next;
1096 
1097 	for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
1098 	     *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
1099 		struct hlist_head *bucket = per_cpu_ptr(head, *cpu);
1100 
1101 		if (!hlist_empty(bucket))
1102 			return bucket->first;
1103 	}
1104 	return NULL;
1105 }
1106 EXPORT_SYMBOL(seq_hlist_next_percpu);
1107 
1108 void __init seq_file_init(void)
1109 {
1110 	seq_file_cache = KMEM_CACHE(seq_file, SLAB_ACCOUNT|SLAB_PANIC);
1111 }
1112