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