xref: /openbmc/linux/fs/seq_file.c (revision aa0dc6a7)
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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10 
11 #include <linux/cache.h>
12 #include <linux/fs.h>
13 #include <linux/export.h>
14 #include <linux/seq_file.h>
15 #include <linux/vmalloc.h>
16 #include <linux/slab.h>
17 #include <linux/cred.h>
18 #include <linux/mm.h>
19 #include <linux/printk.h>
20 #include <linux/string_helpers.h>
21 #include <linux/uio.h>
22 
23 #include <linux/uaccess.h>
24 #include <asm/page.h>
25 
26 static struct kmem_cache *seq_file_cache __ro_after_init;
27 
28 static void seq_set_overflow(struct seq_file *m)
29 {
30 	m->count = m->size;
31 }
32 
33 static void *seq_buf_alloc(unsigned long size)
34 {
35 	return kvmalloc(size, GFP_KERNEL_ACCOUNT);
36 }
37 
38 /**
39  *	seq_open -	initialize sequential file
40  *	@file: file we initialize
41  *	@op: method table describing the sequence
42  *
43  *	seq_open() sets @file, associating it with a sequence described
44  *	by @op.  @op->start() sets the iterator up and returns the first
45  *	element of sequence. @op->stop() shuts it down.  @op->next()
46  *	returns the next element of sequence.  @op->show() prints element
47  *	into the buffer.  In case of error ->start() and ->next() return
48  *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
49  *	returns 0 in case of success and negative number in case of error.
50  *	Returning SEQ_SKIP means "discard this element and move on".
51  *	Note: seq_open() will allocate a struct seq_file and store its
52  *	pointer in @file->private_data. This pointer should not be modified.
53  */
54 int seq_open(struct file *file, const struct seq_operations *op)
55 {
56 	struct seq_file *p;
57 
58 	WARN_ON(file->private_data);
59 
60 	p = kmem_cache_zalloc(seq_file_cache, GFP_KERNEL);
61 	if (!p)
62 		return -ENOMEM;
63 
64 	file->private_data = p;
65 
66 	mutex_init(&p->lock);
67 	p->op = op;
68 
69 	// No refcounting: the lifetime of 'p' is constrained
70 	// to the lifetime of the file.
71 	p->file = file;
72 
73 	/*
74 	 * seq_files support lseek() and pread().  They do not implement
75 	 * write() at all, but we clear FMODE_PWRITE here for historical
76 	 * reasons.
77 	 *
78 	 * If a client of seq_files a) implements file.write() and b) wishes to
79 	 * support pwrite() then that client will need to implement its own
80 	 * file.open() which calls seq_open() and then sets FMODE_PWRITE.
81 	 */
82 	file->f_mode &= ~FMODE_PWRITE;
83 	return 0;
84 }
85 EXPORT_SYMBOL(seq_open);
86 
87 static int traverse(struct seq_file *m, loff_t offset)
88 {
89 	loff_t pos = 0;
90 	int error = 0;
91 	void *p;
92 
93 	m->index = 0;
94 	m->count = m->from = 0;
95 	if (!offset)
96 		return 0;
97 
98 	if (!m->buf) {
99 		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
100 		if (!m->buf)
101 			return -ENOMEM;
102 	}
103 	p = m->op->start(m, &m->index);
104 	while (p) {
105 		error = PTR_ERR(p);
106 		if (IS_ERR(p))
107 			break;
108 		error = m->op->show(m, p);
109 		if (error < 0)
110 			break;
111 		if (unlikely(error)) {
112 			error = 0;
113 			m->count = 0;
114 		}
115 		if (seq_has_overflowed(m))
116 			goto Eoverflow;
117 		p = m->op->next(m, p, &m->index);
118 		if (pos + m->count > offset) {
119 			m->from = offset - pos;
120 			m->count -= m->from;
121 			break;
122 		}
123 		pos += m->count;
124 		m->count = 0;
125 		if (pos == offset)
126 			break;
127 	}
128 	m->op->stop(m, p);
129 	return error;
130 
131 Eoverflow:
132 	m->op->stop(m, p);
133 	kvfree(m->buf);
134 	m->count = 0;
135 	m->buf = seq_buf_alloc(m->size <<= 1);
136 	return !m->buf ? -ENOMEM : -EAGAIN;
137 }
138 
139 /**
140  *	seq_read -	->read() method for sequential files.
141  *	@file: the file to read from
142  *	@buf: the buffer to read to
143  *	@size: the maximum number of bytes to read
144  *	@ppos: the current position in the file
145  *
146  *	Ready-made ->f_op->read()
147  */
148 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
149 {
150 	struct iovec iov = { .iov_base = buf, .iov_len = size};
151 	struct kiocb kiocb;
152 	struct iov_iter iter;
153 	ssize_t ret;
154 
155 	init_sync_kiocb(&kiocb, file);
156 	iov_iter_init(&iter, READ, &iov, 1, size);
157 
158 	kiocb.ki_pos = *ppos;
159 	ret = seq_read_iter(&kiocb, &iter);
160 	*ppos = kiocb.ki_pos;
161 	return ret;
162 }
163 EXPORT_SYMBOL(seq_read);
164 
165 /*
166  * Ready-made ->f_op->read_iter()
167  */
168 ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
169 {
170 	struct seq_file *m = iocb->ki_filp->private_data;
171 	size_t copied = 0;
172 	size_t n;
173 	void *p;
174 	int err = 0;
175 
176 	if (!iov_iter_count(iter))
177 		return 0;
178 
179 	mutex_lock(&m->lock);
180 
181 	/*
182 	 * if request is to read from zero offset, reset iterator to first
183 	 * record as it might have been already advanced by previous requests
184 	 */
185 	if (iocb->ki_pos == 0) {
186 		m->index = 0;
187 		m->count = 0;
188 	}
189 
190 	/* Don't assume ki_pos is where we left it */
191 	if (unlikely(iocb->ki_pos != m->read_pos)) {
192 		while ((err = traverse(m, iocb->ki_pos)) == -EAGAIN)
193 			;
194 		if (err) {
195 			/* With prejudice... */
196 			m->read_pos = 0;
197 			m->index = 0;
198 			m->count = 0;
199 			goto Done;
200 		} else {
201 			m->read_pos = iocb->ki_pos;
202 		}
203 	}
204 
205 	/* grab buffer if we didn't have one */
206 	if (!m->buf) {
207 		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
208 		if (!m->buf)
209 			goto Enomem;
210 	}
211 	// something left in the buffer - copy it out first
212 	if (m->count) {
213 		n = copy_to_iter(m->buf + m->from, m->count, iter);
214 		m->count -= n;
215 		m->from += n;
216 		copied += n;
217 		if (m->count)	// hadn't managed to copy everything
218 			goto Done;
219 	}
220 	// get a non-empty record in the buffer
221 	m->from = 0;
222 	p = m->op->start(m, &m->index);
223 	while (1) {
224 		err = PTR_ERR(p);
225 		if (!p || IS_ERR(p))	// EOF or an error
226 			break;
227 		err = m->op->show(m, p);
228 		if (err < 0)		// hard error
229 			break;
230 		if (unlikely(err))	// ->show() says "skip it"
231 			m->count = 0;
232 		if (unlikely(!m->count)) { // empty record
233 			p = m->op->next(m, p, &m->index);
234 			continue;
235 		}
236 		if (!seq_has_overflowed(m)) // got it
237 			goto Fill;
238 		// need a bigger buffer
239 		m->op->stop(m, p);
240 		kvfree(m->buf);
241 		m->count = 0;
242 		m->buf = seq_buf_alloc(m->size <<= 1);
243 		if (!m->buf)
244 			goto Enomem;
245 		p = m->op->start(m, &m->index);
246 	}
247 	// EOF or an error
248 	m->op->stop(m, p);
249 	m->count = 0;
250 	goto Done;
251 Fill:
252 	// one non-empty record is in the buffer; if they want more,
253 	// try to fit more in, but in any case we need to advance
254 	// the iterator once for every record shown.
255 	while (1) {
256 		size_t offs = m->count;
257 		loff_t pos = m->index;
258 
259 		p = m->op->next(m, p, &m->index);
260 		if (pos == m->index) {
261 			pr_info_ratelimited("buggy .next function %ps did not update position index\n",
262 					    m->op->next);
263 			m->index++;
264 		}
265 		if (!p || IS_ERR(p))	// no next record for us
266 			break;
267 		if (m->count >= iov_iter_count(iter))
268 			break;
269 		err = m->op->show(m, p);
270 		if (err > 0) {		// ->show() says "skip it"
271 			m->count = offs;
272 		} else if (err || seq_has_overflowed(m)) {
273 			m->count = offs;
274 			break;
275 		}
276 	}
277 	m->op->stop(m, p);
278 	n = copy_to_iter(m->buf, m->count, iter);
279 	copied += n;
280 	m->count -= n;
281 	m->from = n;
282 Done:
283 	if (unlikely(!copied)) {
284 		copied = m->count ? -EFAULT : err;
285 	} else {
286 		iocb->ki_pos += copied;
287 		m->read_pos += copied;
288 	}
289 	mutex_unlock(&m->lock);
290 	return copied;
291 Enomem:
292 	err = -ENOMEM;
293 	goto Done;
294 }
295 EXPORT_SYMBOL(seq_read_iter);
296 
297 /**
298  *	seq_lseek -	->llseek() method for sequential files.
299  *	@file: the file in question
300  *	@offset: new position
301  *	@whence: 0 for absolute, 1 for relative position
302  *
303  *	Ready-made ->f_op->llseek()
304  */
305 loff_t seq_lseek(struct file *file, loff_t offset, int whence)
306 {
307 	struct seq_file *m = file->private_data;
308 	loff_t retval = -EINVAL;
309 
310 	mutex_lock(&m->lock);
311 	switch (whence) {
312 	case SEEK_CUR:
313 		offset += file->f_pos;
314 		fallthrough;
315 	case SEEK_SET:
316 		if (offset < 0)
317 			break;
318 		retval = offset;
319 		if (offset != m->read_pos) {
320 			while ((retval = traverse(m, offset)) == -EAGAIN)
321 				;
322 			if (retval) {
323 				/* with extreme prejudice... */
324 				file->f_pos = 0;
325 				m->read_pos = 0;
326 				m->index = 0;
327 				m->count = 0;
328 			} else {
329 				m->read_pos = offset;
330 				retval = file->f_pos = offset;
331 			}
332 		} else {
333 			file->f_pos = offset;
334 		}
335 	}
336 	mutex_unlock(&m->lock);
337 	return retval;
338 }
339 EXPORT_SYMBOL(seq_lseek);
340 
341 /**
342  *	seq_release -	free the structures associated with sequential file.
343  *	@file: file in question
344  *	@inode: its inode
345  *
346  *	Frees the structures associated with sequential file; can be used
347  *	as ->f_op->release() if you don't have private data to destroy.
348  */
349 int seq_release(struct inode *inode, struct file *file)
350 {
351 	struct seq_file *m = file->private_data;
352 	kvfree(m->buf);
353 	kmem_cache_free(seq_file_cache, m);
354 	return 0;
355 }
356 EXPORT_SYMBOL(seq_release);
357 
358 /**
359  * seq_escape_mem - print data into buffer, escaping some characters
360  * @m: target buffer
361  * @src: source buffer
362  * @len: size of source buffer
363  * @flags: flags to pass to string_escape_mem()
364  * @esc: set of characters that need escaping
365  *
366  * Puts data into buffer, replacing each occurrence of character from
367  * given class (defined by @flags and @esc) with printable escaped sequence.
368  *
369  * Use seq_has_overflowed() to check for errors.
370  */
371 void seq_escape_mem(struct seq_file *m, const char *src, size_t len,
372 		    unsigned int flags, const char *esc)
373 {
374 	char *buf;
375 	size_t size = seq_get_buf(m, &buf);
376 	int ret;
377 
378 	ret = string_escape_mem(src, len, buf, size, flags, esc);
379 	seq_commit(m, ret < size ? ret : -1);
380 }
381 EXPORT_SYMBOL(seq_escape_mem);
382 
383 /**
384  *	seq_escape -	print string into buffer, escaping some characters
385  *	@m:	target buffer
386  *	@s:	string
387  *	@esc:	set of characters that need escaping
388  *
389  *	Puts string into buffer, replacing each occurrence of character from
390  *	@esc with usual octal escape.
391  *	Use seq_has_overflowed() to check for errors.
392  */
393 void seq_escape(struct seq_file *m, const char *s, const char *esc)
394 {
395 	seq_escape_str(m, s, ESCAPE_OCTAL, esc);
396 }
397 EXPORT_SYMBOL(seq_escape);
398 
399 void seq_vprintf(struct seq_file *m, const char *f, va_list args)
400 {
401 	int len;
402 
403 	if (m->count < m->size) {
404 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
405 		if (m->count + len < m->size) {
406 			m->count += len;
407 			return;
408 		}
409 	}
410 	seq_set_overflow(m);
411 }
412 EXPORT_SYMBOL(seq_vprintf);
413 
414 void seq_printf(struct seq_file *m, const char *f, ...)
415 {
416 	va_list args;
417 
418 	va_start(args, f);
419 	seq_vprintf(m, f, args);
420 	va_end(args);
421 }
422 EXPORT_SYMBOL(seq_printf);
423 
424 #ifdef CONFIG_BINARY_PRINTF
425 void seq_bprintf(struct seq_file *m, const char *f, const u32 *binary)
426 {
427 	int len;
428 
429 	if (m->count < m->size) {
430 		len = bstr_printf(m->buf + m->count, m->size - m->count, f,
431 				  binary);
432 		if (m->count + len < m->size) {
433 			m->count += len;
434 			return;
435 		}
436 	}
437 	seq_set_overflow(m);
438 }
439 EXPORT_SYMBOL(seq_bprintf);
440 #endif /* CONFIG_BINARY_PRINTF */
441 
442 /**
443  *	mangle_path -	mangle and copy path to buffer beginning
444  *	@s: buffer start
445  *	@p: beginning of path in above buffer
446  *	@esc: set of characters that need escaping
447  *
448  *      Copy the path from @p to @s, replacing each occurrence of character from
449  *      @esc with usual octal escape.
450  *      Returns pointer past last written character in @s, or NULL in case of
451  *      failure.
452  */
453 char *mangle_path(char *s, const char *p, const char *esc)
454 {
455 	while (s <= p) {
456 		char c = *p++;
457 		if (!c) {
458 			return s;
459 		} else if (!strchr(esc, c)) {
460 			*s++ = c;
461 		} else if (s + 4 > p) {
462 			break;
463 		} else {
464 			*s++ = '\\';
465 			*s++ = '0' + ((c & 0300) >> 6);
466 			*s++ = '0' + ((c & 070) >> 3);
467 			*s++ = '0' + (c & 07);
468 		}
469 	}
470 	return NULL;
471 }
472 EXPORT_SYMBOL(mangle_path);
473 
474 /**
475  * seq_path - seq_file interface to print a pathname
476  * @m: the seq_file handle
477  * @path: the struct path to print
478  * @esc: set of characters to escape in the output
479  *
480  * return the absolute path of 'path', as represented by the
481  * dentry / mnt pair in the path parameter.
482  */
483 int seq_path(struct seq_file *m, const struct path *path, const char *esc)
484 {
485 	char *buf;
486 	size_t size = seq_get_buf(m, &buf);
487 	int res = -1;
488 
489 	if (size) {
490 		char *p = d_path(path, buf, size);
491 		if (!IS_ERR(p)) {
492 			char *end = mangle_path(buf, p, esc);
493 			if (end)
494 				res = end - buf;
495 		}
496 	}
497 	seq_commit(m, res);
498 
499 	return res;
500 }
501 EXPORT_SYMBOL(seq_path);
502 
503 /**
504  * seq_file_path - seq_file interface to print a pathname of a file
505  * @m: the seq_file handle
506  * @file: the struct file to print
507  * @esc: set of characters to escape in the output
508  *
509  * return the absolute path to the file.
510  */
511 int seq_file_path(struct seq_file *m, struct file *file, const char *esc)
512 {
513 	return seq_path(m, &file->f_path, esc);
514 }
515 EXPORT_SYMBOL(seq_file_path);
516 
517 /*
518  * Same as seq_path, but relative to supplied root.
519  */
520 int seq_path_root(struct seq_file *m, const struct path *path,
521 		  const struct path *root, const char *esc)
522 {
523 	char *buf;
524 	size_t size = seq_get_buf(m, &buf);
525 	int res = -ENAMETOOLONG;
526 
527 	if (size) {
528 		char *p;
529 
530 		p = __d_path(path, root, buf, size);
531 		if (!p)
532 			return SEQ_SKIP;
533 		res = PTR_ERR(p);
534 		if (!IS_ERR(p)) {
535 			char *end = mangle_path(buf, p, esc);
536 			if (end)
537 				res = end - buf;
538 			else
539 				res = -ENAMETOOLONG;
540 		}
541 	}
542 	seq_commit(m, res);
543 
544 	return res < 0 && res != -ENAMETOOLONG ? res : 0;
545 }
546 
547 /*
548  * returns the path of the 'dentry' from the root of its filesystem.
549  */
550 int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)
551 {
552 	char *buf;
553 	size_t size = seq_get_buf(m, &buf);
554 	int res = -1;
555 
556 	if (size) {
557 		char *p = dentry_path(dentry, buf, size);
558 		if (!IS_ERR(p)) {
559 			char *end = mangle_path(buf, p, esc);
560 			if (end)
561 				res = end - buf;
562 		}
563 	}
564 	seq_commit(m, res);
565 
566 	return res;
567 }
568 EXPORT_SYMBOL(seq_dentry);
569 
570 static void *single_start(struct seq_file *p, loff_t *pos)
571 {
572 	return NULL + (*pos == 0);
573 }
574 
575 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
576 {
577 	++*pos;
578 	return NULL;
579 }
580 
581 static void single_stop(struct seq_file *p, void *v)
582 {
583 }
584 
585 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
586 		void *data)
587 {
588 	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL_ACCOUNT);
589 	int res = -ENOMEM;
590 
591 	if (op) {
592 		op->start = single_start;
593 		op->next = single_next;
594 		op->stop = single_stop;
595 		op->show = show;
596 		res = seq_open(file, op);
597 		if (!res)
598 			((struct seq_file *)file->private_data)->private = data;
599 		else
600 			kfree(op);
601 	}
602 	return res;
603 }
604 EXPORT_SYMBOL(single_open);
605 
606 int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
607 		void *data, size_t size)
608 {
609 	char *buf = seq_buf_alloc(size);
610 	int ret;
611 	if (!buf)
612 		return -ENOMEM;
613 	ret = single_open(file, show, data);
614 	if (ret) {
615 		kvfree(buf);
616 		return ret;
617 	}
618 	((struct seq_file *)file->private_data)->buf = buf;
619 	((struct seq_file *)file->private_data)->size = size;
620 	return 0;
621 }
622 EXPORT_SYMBOL(single_open_size);
623 
624 int single_release(struct inode *inode, struct file *file)
625 {
626 	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
627 	int res = seq_release(inode, file);
628 	kfree(op);
629 	return res;
630 }
631 EXPORT_SYMBOL(single_release);
632 
633 int seq_release_private(struct inode *inode, struct file *file)
634 {
635 	struct seq_file *seq = file->private_data;
636 
637 	kfree(seq->private);
638 	seq->private = NULL;
639 	return seq_release(inode, file);
640 }
641 EXPORT_SYMBOL(seq_release_private);
642 
643 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
644 		int psize)
645 {
646 	int rc;
647 	void *private;
648 	struct seq_file *seq;
649 
650 	private = kzalloc(psize, GFP_KERNEL_ACCOUNT);
651 	if (private == NULL)
652 		goto out;
653 
654 	rc = seq_open(f, ops);
655 	if (rc < 0)
656 		goto out_free;
657 
658 	seq = f->private_data;
659 	seq->private = private;
660 	return private;
661 
662 out_free:
663 	kfree(private);
664 out:
665 	return NULL;
666 }
667 EXPORT_SYMBOL(__seq_open_private);
668 
669 int seq_open_private(struct file *filp, const struct seq_operations *ops,
670 		int psize)
671 {
672 	return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
673 }
674 EXPORT_SYMBOL(seq_open_private);
675 
676 void seq_putc(struct seq_file *m, char c)
677 {
678 	if (m->count >= m->size)
679 		return;
680 
681 	m->buf[m->count++] = c;
682 }
683 EXPORT_SYMBOL(seq_putc);
684 
685 void seq_puts(struct seq_file *m, const char *s)
686 {
687 	int len = strlen(s);
688 
689 	if (m->count + len >= m->size) {
690 		seq_set_overflow(m);
691 		return;
692 	}
693 	memcpy(m->buf + m->count, s, len);
694 	m->count += len;
695 }
696 EXPORT_SYMBOL(seq_puts);
697 
698 /**
699  * seq_put_decimal_ull_width - A helper routine for putting decimal numbers
700  * 			       without rich format of printf().
701  * only 'unsigned long long' is supported.
702  * @m: seq_file identifying the buffer to which data should be written
703  * @delimiter: a string which is printed before the number
704  * @num: the number
705  * @width: a minimum field width
706  *
707  * This routine will put strlen(delimiter) + number into seq_filed.
708  * This routine is very quick when you show lots of numbers.
709  * In usual cases, it will be better to use seq_printf(). It's easier to read.
710  */
711 void seq_put_decimal_ull_width(struct seq_file *m, const char *delimiter,
712 			 unsigned long long num, unsigned int width)
713 {
714 	int len;
715 
716 	if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
717 		goto overflow;
718 
719 	if (delimiter && delimiter[0]) {
720 		if (delimiter[1] == 0)
721 			seq_putc(m, delimiter[0]);
722 		else
723 			seq_puts(m, delimiter);
724 	}
725 
726 	if (!width)
727 		width = 1;
728 
729 	if (m->count + width >= m->size)
730 		goto overflow;
731 
732 	len = num_to_str(m->buf + m->count, m->size - m->count, num, width);
733 	if (!len)
734 		goto overflow;
735 
736 	m->count += len;
737 	return;
738 
739 overflow:
740 	seq_set_overflow(m);
741 }
742 
743 void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,
744 			 unsigned long long num)
745 {
746 	return seq_put_decimal_ull_width(m, delimiter, num, 0);
747 }
748 EXPORT_SYMBOL(seq_put_decimal_ull);
749 
750 /**
751  * seq_put_hex_ll - put a number in hexadecimal notation
752  * @m: seq_file identifying the buffer to which data should be written
753  * @delimiter: a string which is printed before the number
754  * @v: the number
755  * @width: a minimum field width
756  *
757  * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "%08llx", v)
758  *
759  * This routine is very quick when you show lots of numbers.
760  * In usual cases, it will be better to use seq_printf(). It's easier to read.
761  */
762 void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
763 				unsigned long long v, unsigned int width)
764 {
765 	unsigned int len;
766 	int i;
767 
768 	if (delimiter && delimiter[0]) {
769 		if (delimiter[1] == 0)
770 			seq_putc(m, delimiter[0]);
771 		else
772 			seq_puts(m, delimiter);
773 	}
774 
775 	/* If x is 0, the result of __builtin_clzll is undefined */
776 	if (v == 0)
777 		len = 1;
778 	else
779 		len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
780 
781 	if (len < width)
782 		len = width;
783 
784 	if (m->count + len > m->size) {
785 		seq_set_overflow(m);
786 		return;
787 	}
788 
789 	for (i = len - 1; i >= 0; i--) {
790 		m->buf[m->count + i] = hex_asc[0xf & v];
791 		v = v >> 4;
792 	}
793 	m->count += len;
794 }
795 
796 void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num)
797 {
798 	int len;
799 
800 	if (m->count + 3 >= m->size) /* we'll write 2 bytes at least */
801 		goto overflow;
802 
803 	if (delimiter && delimiter[0]) {
804 		if (delimiter[1] == 0)
805 			seq_putc(m, delimiter[0]);
806 		else
807 			seq_puts(m, delimiter);
808 	}
809 
810 	if (m->count + 2 >= m->size)
811 		goto overflow;
812 
813 	if (num < 0) {
814 		m->buf[m->count++] = '-';
815 		num = -num;
816 	}
817 
818 	if (num < 10) {
819 		m->buf[m->count++] = num + '0';
820 		return;
821 	}
822 
823 	len = num_to_str(m->buf + m->count, m->size - m->count, num, 0);
824 	if (!len)
825 		goto overflow;
826 
827 	m->count += len;
828 	return;
829 
830 overflow:
831 	seq_set_overflow(m);
832 }
833 EXPORT_SYMBOL(seq_put_decimal_ll);
834 
835 /**
836  * seq_write - write arbitrary data to buffer
837  * @seq: seq_file identifying the buffer to which data should be written
838  * @data: data address
839  * @len: number of bytes
840  *
841  * Return 0 on success, non-zero otherwise.
842  */
843 int seq_write(struct seq_file *seq, const void *data, size_t len)
844 {
845 	if (seq->count + len < seq->size) {
846 		memcpy(seq->buf + seq->count, data, len);
847 		seq->count += len;
848 		return 0;
849 	}
850 	seq_set_overflow(seq);
851 	return -1;
852 }
853 EXPORT_SYMBOL(seq_write);
854 
855 /**
856  * seq_pad - write padding spaces to buffer
857  * @m: seq_file identifying the buffer to which data should be written
858  * @c: the byte to append after padding if non-zero
859  */
860 void seq_pad(struct seq_file *m, char c)
861 {
862 	int size = m->pad_until - m->count;
863 	if (size > 0) {
864 		if (size + m->count > m->size) {
865 			seq_set_overflow(m);
866 			return;
867 		}
868 		memset(m->buf + m->count, ' ', size);
869 		m->count += size;
870 	}
871 	if (c)
872 		seq_putc(m, c);
873 }
874 EXPORT_SYMBOL(seq_pad);
875 
876 /* A complete analogue of print_hex_dump() */
877 void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
878 		  int rowsize, int groupsize, const void *buf, size_t len,
879 		  bool ascii)
880 {
881 	const u8 *ptr = buf;
882 	int i, linelen, remaining = len;
883 	char *buffer;
884 	size_t size;
885 	int ret;
886 
887 	if (rowsize != 16 && rowsize != 32)
888 		rowsize = 16;
889 
890 	for (i = 0; i < len && !seq_has_overflowed(m); i += rowsize) {
891 		linelen = min(remaining, rowsize);
892 		remaining -= rowsize;
893 
894 		switch (prefix_type) {
895 		case DUMP_PREFIX_ADDRESS:
896 			seq_printf(m, "%s%p: ", prefix_str, ptr + i);
897 			break;
898 		case DUMP_PREFIX_OFFSET:
899 			seq_printf(m, "%s%.8x: ", prefix_str, i);
900 			break;
901 		default:
902 			seq_printf(m, "%s", prefix_str);
903 			break;
904 		}
905 
906 		size = seq_get_buf(m, &buffer);
907 		ret = hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
908 					 buffer, size, ascii);
909 		seq_commit(m, ret < size ? ret : -1);
910 
911 		seq_putc(m, '\n');
912 	}
913 }
914 EXPORT_SYMBOL(seq_hex_dump);
915 
916 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
917 {
918 	struct list_head *lh;
919 
920 	list_for_each(lh, head)
921 		if (pos-- == 0)
922 			return lh;
923 
924 	return NULL;
925 }
926 EXPORT_SYMBOL(seq_list_start);
927 
928 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
929 {
930 	if (!pos)
931 		return head;
932 
933 	return seq_list_start(head, pos - 1);
934 }
935 EXPORT_SYMBOL(seq_list_start_head);
936 
937 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
938 {
939 	struct list_head *lh;
940 
941 	lh = ((struct list_head *)v)->next;
942 	++*ppos;
943 	return lh == head ? NULL : lh;
944 }
945 EXPORT_SYMBOL(seq_list_next);
946 
947 /**
948  * seq_hlist_start - start an iteration of a hlist
949  * @head: the head of the hlist
950  * @pos:  the start position of the sequence
951  *
952  * Called at seq_file->op->start().
953  */
954 struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
955 {
956 	struct hlist_node *node;
957 
958 	hlist_for_each(node, head)
959 		if (pos-- == 0)
960 			return node;
961 	return NULL;
962 }
963 EXPORT_SYMBOL(seq_hlist_start);
964 
965 /**
966  * seq_hlist_start_head - start an iteration of a hlist
967  * @head: the head of the hlist
968  * @pos:  the start position of the sequence
969  *
970  * Called at seq_file->op->start(). Call this function if you want to
971  * print a header at the top of the output.
972  */
973 struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
974 {
975 	if (!pos)
976 		return SEQ_START_TOKEN;
977 
978 	return seq_hlist_start(head, pos - 1);
979 }
980 EXPORT_SYMBOL(seq_hlist_start_head);
981 
982 /**
983  * seq_hlist_next - move to the next position of the hlist
984  * @v:    the current iterator
985  * @head: the head of the hlist
986  * @ppos: the current position
987  *
988  * Called at seq_file->op->next().
989  */
990 struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
991 				  loff_t *ppos)
992 {
993 	struct hlist_node *node = v;
994 
995 	++*ppos;
996 	if (v == SEQ_START_TOKEN)
997 		return head->first;
998 	else
999 		return node->next;
1000 }
1001 EXPORT_SYMBOL(seq_hlist_next);
1002 
1003 /**
1004  * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
1005  * @head: the head of the hlist
1006  * @pos:  the start position of the sequence
1007  *
1008  * Called at seq_file->op->start().
1009  *
1010  * This list-traversal primitive may safely run concurrently with
1011  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
1012  * as long as the traversal is guarded by rcu_read_lock().
1013  */
1014 struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
1015 				       loff_t pos)
1016 {
1017 	struct hlist_node *node;
1018 
1019 	__hlist_for_each_rcu(node, head)
1020 		if (pos-- == 0)
1021 			return node;
1022 	return NULL;
1023 }
1024 EXPORT_SYMBOL(seq_hlist_start_rcu);
1025 
1026 /**
1027  * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
1028  * @head: the head of the hlist
1029  * @pos:  the start position of the sequence
1030  *
1031  * Called at seq_file->op->start(). Call this function if you want to
1032  * print a header at the top of the output.
1033  *
1034  * This list-traversal primitive may safely run concurrently with
1035  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
1036  * as long as the traversal is guarded by rcu_read_lock().
1037  */
1038 struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
1039 					    loff_t pos)
1040 {
1041 	if (!pos)
1042 		return SEQ_START_TOKEN;
1043 
1044 	return seq_hlist_start_rcu(head, pos - 1);
1045 }
1046 EXPORT_SYMBOL(seq_hlist_start_head_rcu);
1047 
1048 /**
1049  * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
1050  * @v:    the current iterator
1051  * @head: the head of the hlist
1052  * @ppos: the current position
1053  *
1054  * Called at seq_file->op->next().
1055  *
1056  * This list-traversal primitive may safely run concurrently with
1057  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
1058  * as long as the traversal is guarded by rcu_read_lock().
1059  */
1060 struct hlist_node *seq_hlist_next_rcu(void *v,
1061 				      struct hlist_head *head,
1062 				      loff_t *ppos)
1063 {
1064 	struct hlist_node *node = v;
1065 
1066 	++*ppos;
1067 	if (v == SEQ_START_TOKEN)
1068 		return rcu_dereference(head->first);
1069 	else
1070 		return rcu_dereference(node->next);
1071 }
1072 EXPORT_SYMBOL(seq_hlist_next_rcu);
1073 
1074 /**
1075  * seq_hlist_start_percpu - start an iteration of a percpu hlist array
1076  * @head: pointer to percpu array of struct hlist_heads
1077  * @cpu:  pointer to cpu "cursor"
1078  * @pos:  start position of sequence
1079  *
1080  * Called at seq_file->op->start().
1081  */
1082 struct hlist_node *
1083 seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
1084 {
1085 	struct hlist_node *node;
1086 
1087 	for_each_possible_cpu(*cpu) {
1088 		hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
1089 			if (pos-- == 0)
1090 				return node;
1091 		}
1092 	}
1093 	return NULL;
1094 }
1095 EXPORT_SYMBOL(seq_hlist_start_percpu);
1096 
1097 /**
1098  * seq_hlist_next_percpu - move to the next position of the percpu hlist array
1099  * @v:    pointer to current hlist_node
1100  * @head: pointer to percpu array of struct hlist_heads
1101  * @cpu:  pointer to cpu "cursor"
1102  * @pos:  start position of sequence
1103  *
1104  * Called at seq_file->op->next().
1105  */
1106 struct hlist_node *
1107 seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
1108 			int *cpu, loff_t *pos)
1109 {
1110 	struct hlist_node *node = v;
1111 
1112 	++*pos;
1113 
1114 	if (node->next)
1115 		return node->next;
1116 
1117 	for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
1118 	     *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
1119 		struct hlist_head *bucket = per_cpu_ptr(head, *cpu);
1120 
1121 		if (!hlist_empty(bucket))
1122 			return bucket->first;
1123 	}
1124 	return NULL;
1125 }
1126 EXPORT_SYMBOL(seq_hlist_next_percpu);
1127 
1128 void __init seq_file_init(void)
1129 {
1130 	seq_file_cache = KMEM_CACHE(seq_file, SLAB_ACCOUNT|SLAB_PANIC);
1131 }
1132