1 // SPDX-License-Identifier: GPL-2.0
5 * helper functions for making synthetic files from sequences of records.
6 * initial implementation -- AV, Oct 2001.
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/cache.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>
19 #include <linux/printk.h>
20 #include <linux/string_helpers.h>
21 #include <linux/uio.h>
23 #include <linux/uaccess.h>
26 static struct kmem_cache *seq_file_cache __ro_after_init;
28 static void seq_set_overflow(struct seq_file *m)
33 static void *seq_buf_alloc(unsigned long size)
35 if (unlikely(size > MAX_RW_COUNT))
38 return kvmalloc(size, GFP_KERNEL_ACCOUNT);
42 * seq_open - initialize sequential file
43 * @file: file we initialize
44 * @op: method table describing the sequence
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.
57 int seq_open(struct file *file, const struct seq_operations *op)
61 WARN_ON(file->private_data);
63 p = kmem_cache_zalloc(seq_file_cache, GFP_KERNEL);
67 file->private_data = p;
72 // No refcounting: the lifetime of 'p' is constrained
73 // to the lifetime of the file.
77 * seq_files support lseek() and pread(). They do not implement
78 * write() at all, but we clear FMODE_PWRITE here for historical
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.
85 file->f_mode &= ~FMODE_PWRITE;
88 EXPORT_SYMBOL(seq_open);
90 static int traverse(struct seq_file *m, loff_t offset)
97 m->count = m->from = 0;
102 m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
106 p = m->op->start(m, &m->index);
111 error = m->op->show(m, p);
114 if (unlikely(error)) {
118 if (seq_has_overflowed(m))
120 p = m->op->next(m, p, &m->index);
121 if (pos + m->count > offset) {
122 m->from = offset - pos;
138 m->buf = seq_buf_alloc(m->size <<= 1);
139 return !m->buf ? -ENOMEM : -EAGAIN;
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
149 * Ready-made ->f_op->read()
151 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
153 struct iovec iov = { .iov_base = buf, .iov_len = size};
155 struct iov_iter iter;
158 init_sync_kiocb(&kiocb, file);
159 iov_iter_init(&iter, READ, &iov, 1, size);
161 kiocb.ki_pos = *ppos;
162 ret = seq_read_iter(&kiocb, &iter);
163 *ppos = kiocb.ki_pos;
166 EXPORT_SYMBOL(seq_read);
169 * Ready-made ->f_op->read_iter()
171 ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
173 struct seq_file *m = iocb->ki_filp->private_data;
179 if (!iov_iter_count(iter))
182 mutex_lock(&m->lock);
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
188 if (iocb->ki_pos == 0) {
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)
198 /* With prejudice... */
204 m->read_pos = iocb->ki_pos;
208 /* grab buffer if we didn't have one */
210 m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
214 // something left in the buffer - copy it out first
216 n = copy_to_iter(m->buf + m->from, m->count, iter);
220 if (m->count) // hadn't managed to copy everything
223 // get a non-empty record in the buffer
225 p = m->op->start(m, &m->index);
228 if (!p || IS_ERR(p)) // EOF or an error
230 err = m->op->show(m, p);
231 if (err < 0) // hard error
233 if (unlikely(err)) // ->show() says "skip it"
235 if (unlikely(!m->count)) { // empty record
236 p = m->op->next(m, p, &m->index);
239 if (!seq_has_overflowed(m)) // got it
241 // need a bigger buffer
245 m->buf = seq_buf_alloc(m->size <<= 1);
248 p = m->op->start(m, &m->index);
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.
259 size_t offs = m->count;
260 loff_t pos = m->index;
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",
268 if (!p || IS_ERR(p)) // no next record for us
270 if (m->count >= iov_iter_count(iter))
272 err = m->op->show(m, p);
273 if (err > 0) { // ->show() says "skip it"
275 } else if (err || seq_has_overflowed(m)) {
281 n = copy_to_iter(m->buf, m->count, iter);
286 if (unlikely(!copied)) {
287 copied = m->count ? -EFAULT : err;
289 iocb->ki_pos += copied;
290 m->read_pos += copied;
292 mutex_unlock(&m->lock);
298 EXPORT_SYMBOL(seq_read_iter);
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
306 * Ready-made ->f_op->llseek()
308 loff_t seq_lseek(struct file *file, loff_t offset, int whence)
310 struct seq_file *m = file->private_data;
311 loff_t retval = -EINVAL;
313 mutex_lock(&m->lock);
316 offset += file->f_pos;
322 if (offset != m->read_pos) {
323 while ((retval = traverse(m, offset)) == -EAGAIN)
326 /* with extreme prejudice... */
332 m->read_pos = offset;
333 retval = file->f_pos = offset;
336 file->f_pos = offset;
339 mutex_unlock(&m->lock);
342 EXPORT_SYMBOL(seq_lseek);
345 * seq_release - free the structures associated with sequential file.
346 * @file: file in question
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.
352 int seq_release(struct inode *inode, struct file *file)
354 struct seq_file *m = file->private_data;
356 kmem_cache_free(seq_file_cache, m);
359 EXPORT_SYMBOL(seq_release);
362 * seq_escape - print string into buffer, escaping some characters
365 * @esc: set of characters that need escaping
367 * Puts string into buffer, replacing each occurrence of character from
368 * @esc with usual octal escape.
369 * Use seq_has_overflowed() to check for errors.
371 void seq_escape(struct seq_file *m, const char *s, const char *esc)
374 size_t size = seq_get_buf(m, &buf);
377 ret = string_escape_str(s, buf, size, ESCAPE_OCTAL, esc);
378 seq_commit(m, ret < size ? ret : -1);
380 EXPORT_SYMBOL(seq_escape);
382 void seq_escape_mem_ascii(struct seq_file *m, const char *src, size_t isz)
385 size_t size = seq_get_buf(m, &buf);
388 ret = string_escape_mem_ascii(src, isz, buf, size);
389 seq_commit(m, ret < size ? ret : -1);
391 EXPORT_SYMBOL(seq_escape_mem_ascii);
393 void seq_vprintf(struct seq_file *m, const char *f, va_list args)
397 if (m->count < m->size) {
398 len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
399 if (m->count + len < m->size) {
406 EXPORT_SYMBOL(seq_vprintf);
408 void seq_printf(struct seq_file *m, const char *f, ...)
413 seq_vprintf(m, f, args);
416 EXPORT_SYMBOL(seq_printf);
419 * mangle_path - mangle and copy path to buffer beginning
421 * @p: beginning of path in above buffer
422 * @esc: set of characters that need escaping
424 * Copy the path from @p to @s, replacing each occurrence of character from
425 * @esc with usual octal escape.
426 * Returns pointer past last written character in @s, or NULL in case of
429 char *mangle_path(char *s, const char *p, const char *esc)
435 } else if (!strchr(esc, c)) {
437 } else if (s + 4 > p) {
441 *s++ = '0' + ((c & 0300) >> 6);
442 *s++ = '0' + ((c & 070) >> 3);
443 *s++ = '0' + (c & 07);
448 EXPORT_SYMBOL(mangle_path);
451 * seq_path - seq_file interface to print a pathname
452 * @m: the seq_file handle
453 * @path: the struct path to print
454 * @esc: set of characters to escape in the output
456 * return the absolute path of 'path', as represented by the
457 * dentry / mnt pair in the path parameter.
459 int seq_path(struct seq_file *m, const struct path *path, const char *esc)
462 size_t size = seq_get_buf(m, &buf);
466 char *p = d_path(path, buf, size);
468 char *end = mangle_path(buf, p, esc);
477 EXPORT_SYMBOL(seq_path);
480 * seq_file_path - seq_file interface to print a pathname of a file
481 * @m: the seq_file handle
482 * @file: the struct file to print
483 * @esc: set of characters to escape in the output
485 * return the absolute path to the file.
487 int seq_file_path(struct seq_file *m, struct file *file, const char *esc)
489 return seq_path(m, &file->f_path, esc);
491 EXPORT_SYMBOL(seq_file_path);
494 * Same as seq_path, but relative to supplied root.
496 int seq_path_root(struct seq_file *m, const struct path *path,
497 const struct path *root, const char *esc)
500 size_t size = seq_get_buf(m, &buf);
501 int res = -ENAMETOOLONG;
506 p = __d_path(path, root, buf, size);
511 char *end = mangle_path(buf, p, esc);
520 return res < 0 && res != -ENAMETOOLONG ? res : 0;
524 * returns the path of the 'dentry' from the root of its filesystem.
526 int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)
529 size_t size = seq_get_buf(m, &buf);
533 char *p = dentry_path(dentry, buf, size);
535 char *end = mangle_path(buf, p, esc);
544 EXPORT_SYMBOL(seq_dentry);
546 static void *single_start(struct seq_file *p, loff_t *pos)
548 return NULL + (*pos == 0);
551 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
557 static void single_stop(struct seq_file *p, void *v)
561 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
564 struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL_ACCOUNT);
568 op->start = single_start;
569 op->next = single_next;
570 op->stop = single_stop;
572 res = seq_open(file, op);
574 ((struct seq_file *)file->private_data)->private = data;
580 EXPORT_SYMBOL(single_open);
582 int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
583 void *data, size_t size)
585 char *buf = seq_buf_alloc(size);
589 ret = single_open(file, show, data);
594 ((struct seq_file *)file->private_data)->buf = buf;
595 ((struct seq_file *)file->private_data)->size = size;
598 EXPORT_SYMBOL(single_open_size);
600 int single_release(struct inode *inode, struct file *file)
602 const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
603 int res = seq_release(inode, file);
607 EXPORT_SYMBOL(single_release);
609 int seq_release_private(struct inode *inode, struct file *file)
611 struct seq_file *seq = file->private_data;
615 return seq_release(inode, file);
617 EXPORT_SYMBOL(seq_release_private);
619 void *__seq_open_private(struct file *f, const struct seq_operations *ops,
624 struct seq_file *seq;
626 private = kzalloc(psize, GFP_KERNEL_ACCOUNT);
630 rc = seq_open(f, ops);
634 seq = f->private_data;
635 seq->private = private;
643 EXPORT_SYMBOL(__seq_open_private);
645 int seq_open_private(struct file *filp, const struct seq_operations *ops,
648 return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
650 EXPORT_SYMBOL(seq_open_private);
652 void seq_putc(struct seq_file *m, char c)
654 if (m->count >= m->size)
657 m->buf[m->count++] = c;
659 EXPORT_SYMBOL(seq_putc);
661 void seq_puts(struct seq_file *m, const char *s)
665 if (m->count + len >= m->size) {
669 memcpy(m->buf + m->count, s, len);
672 EXPORT_SYMBOL(seq_puts);
675 * A helper routine for putting decimal numbers without rich format of printf().
676 * only 'unsigned long long' is supported.
677 * @m: seq_file identifying the buffer to which data should be written
678 * @delimiter: a string which is printed before the number
680 * @width: a minimum field width
682 * This routine will put strlen(delimiter) + number into seq_filed.
683 * This routine is very quick when you show lots of numbers.
684 * In usual cases, it will be better to use seq_printf(). It's easier to read.
686 void seq_put_decimal_ull_width(struct seq_file *m, const char *delimiter,
687 unsigned long long num, unsigned int width)
691 if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
694 if (delimiter && delimiter[0]) {
695 if (delimiter[1] == 0)
696 seq_putc(m, delimiter[0]);
698 seq_puts(m, delimiter);
704 if (m->count + width >= m->size)
707 len = num_to_str(m->buf + m->count, m->size - m->count, num, width);
718 void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,
719 unsigned long long num)
721 return seq_put_decimal_ull_width(m, delimiter, num, 0);
723 EXPORT_SYMBOL(seq_put_decimal_ull);
726 * seq_put_hex_ll - put a number in hexadecimal notation
727 * @m: seq_file identifying the buffer to which data should be written
728 * @delimiter: a string which is printed before the number
730 * @width: a minimum field width
732 * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "%08llx", v)
734 * This routine is very quick when you show lots of numbers.
735 * In usual cases, it will be better to use seq_printf(). It's easier to read.
737 void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
738 unsigned long long v, unsigned int width)
743 if (delimiter && delimiter[0]) {
744 if (delimiter[1] == 0)
745 seq_putc(m, delimiter[0]);
747 seq_puts(m, delimiter);
750 /* If x is 0, the result of __builtin_clzll is undefined */
754 len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
759 if (m->count + len > m->size) {
764 for (i = len - 1; i >= 0; i--) {
765 m->buf[m->count + i] = hex_asc[0xf & v];
771 void seq_put_decimal_ll(struct seq_file *m, const char *delimiter, long long num)
775 if (m->count + 3 >= m->size) /* we'll write 2 bytes at least */
778 if (delimiter && delimiter[0]) {
779 if (delimiter[1] == 0)
780 seq_putc(m, delimiter[0]);
782 seq_puts(m, delimiter);
785 if (m->count + 2 >= m->size)
789 m->buf[m->count++] = '-';
794 m->buf[m->count++] = num + '0';
798 len = num_to_str(m->buf + m->count, m->size - m->count, num, 0);
808 EXPORT_SYMBOL(seq_put_decimal_ll);
811 * seq_write - write arbitrary data to buffer
812 * @seq: seq_file identifying the buffer to which data should be written
813 * @data: data address
814 * @len: number of bytes
816 * Return 0 on success, non-zero otherwise.
818 int seq_write(struct seq_file *seq, const void *data, size_t len)
820 if (seq->count + len < seq->size) {
821 memcpy(seq->buf + seq->count, data, len);
825 seq_set_overflow(seq);
828 EXPORT_SYMBOL(seq_write);
831 * seq_pad - write padding spaces to buffer
832 * @m: seq_file identifying the buffer to which data should be written
833 * @c: the byte to append after padding if non-zero
835 void seq_pad(struct seq_file *m, char c)
837 int size = m->pad_until - m->count;
839 if (size + m->count > m->size) {
843 memset(m->buf + m->count, ' ', size);
849 EXPORT_SYMBOL(seq_pad);
851 /* A complete analogue of print_hex_dump() */
852 void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
853 int rowsize, int groupsize, const void *buf, size_t len,
857 int i, linelen, remaining = len;
862 if (rowsize != 16 && rowsize != 32)
865 for (i = 0; i < len && !seq_has_overflowed(m); i += rowsize) {
866 linelen = min(remaining, rowsize);
867 remaining -= rowsize;
869 switch (prefix_type) {
870 case DUMP_PREFIX_ADDRESS:
871 seq_printf(m, "%s%p: ", prefix_str, ptr + i);
873 case DUMP_PREFIX_OFFSET:
874 seq_printf(m, "%s%.8x: ", prefix_str, i);
877 seq_printf(m, "%s", prefix_str);
881 size = seq_get_buf(m, &buffer);
882 ret = hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
883 buffer, size, ascii);
884 seq_commit(m, ret < size ? ret : -1);
889 EXPORT_SYMBOL(seq_hex_dump);
891 struct list_head *seq_list_start(struct list_head *head, loff_t pos)
893 struct list_head *lh;
895 list_for_each(lh, head)
901 EXPORT_SYMBOL(seq_list_start);
903 struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
908 return seq_list_start(head, pos - 1);
910 EXPORT_SYMBOL(seq_list_start_head);
912 struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
914 struct list_head *lh;
916 lh = ((struct list_head *)v)->next;
918 return lh == head ? NULL : lh;
920 EXPORT_SYMBOL(seq_list_next);
923 * seq_hlist_start - start an iteration of a hlist
924 * @head: the head of the hlist
925 * @pos: the start position of the sequence
927 * Called at seq_file->op->start().
929 struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
931 struct hlist_node *node;
933 hlist_for_each(node, head)
938 EXPORT_SYMBOL(seq_hlist_start);
941 * seq_hlist_start_head - start an iteration of a hlist
942 * @head: the head of the hlist
943 * @pos: the start position of the sequence
945 * Called at seq_file->op->start(). Call this function if you want to
946 * print a header at the top of the output.
948 struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
951 return SEQ_START_TOKEN;
953 return seq_hlist_start(head, pos - 1);
955 EXPORT_SYMBOL(seq_hlist_start_head);
958 * seq_hlist_next - move to the next position of the hlist
959 * @v: the current iterator
960 * @head: the head of the hlist
961 * @ppos: the current position
963 * Called at seq_file->op->next().
965 struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
968 struct hlist_node *node = v;
971 if (v == SEQ_START_TOKEN)
976 EXPORT_SYMBOL(seq_hlist_next);
979 * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
980 * @head: the head of the hlist
981 * @pos: the start position of the sequence
983 * Called at seq_file->op->start().
985 * This list-traversal primitive may safely run concurrently with
986 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
987 * as long as the traversal is guarded by rcu_read_lock().
989 struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
992 struct hlist_node *node;
994 __hlist_for_each_rcu(node, head)
999 EXPORT_SYMBOL(seq_hlist_start_rcu);
1002 * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
1003 * @head: the head of the hlist
1004 * @pos: the start position of the sequence
1006 * Called at seq_file->op->start(). Call this function if you want to
1007 * print a header at the top of the output.
1009 * This list-traversal primitive may safely run concurrently with
1010 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
1011 * as long as the traversal is guarded by rcu_read_lock().
1013 struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
1017 return SEQ_START_TOKEN;
1019 return seq_hlist_start_rcu(head, pos - 1);
1021 EXPORT_SYMBOL(seq_hlist_start_head_rcu);
1024 * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
1025 * @v: the current iterator
1026 * @head: the head of the hlist
1027 * @ppos: the current position
1029 * Called at seq_file->op->next().
1031 * This list-traversal primitive may safely run concurrently with
1032 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
1033 * as long as the traversal is guarded by rcu_read_lock().
1035 struct hlist_node *seq_hlist_next_rcu(void *v,
1036 struct hlist_head *head,
1039 struct hlist_node *node = v;
1042 if (v == SEQ_START_TOKEN)
1043 return rcu_dereference(head->first);
1045 return rcu_dereference(node->next);
1047 EXPORT_SYMBOL(seq_hlist_next_rcu);
1050 * seq_hlist_start_precpu - start an iteration of a percpu hlist array
1051 * @head: pointer to percpu array of struct hlist_heads
1052 * @cpu: pointer to cpu "cursor"
1053 * @pos: start position of sequence
1055 * Called at seq_file->op->start().
1058 seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
1060 struct hlist_node *node;
1062 for_each_possible_cpu(*cpu) {
1063 hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
1070 EXPORT_SYMBOL(seq_hlist_start_percpu);
1073 * seq_hlist_next_percpu - move to the next position of the percpu hlist array
1074 * @v: pointer to current hlist_node
1075 * @head: pointer to percpu array of struct hlist_heads
1076 * @cpu: pointer to cpu "cursor"
1077 * @pos: start position of sequence
1079 * Called at seq_file->op->next().
1082 seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
1083 int *cpu, loff_t *pos)
1085 struct hlist_node *node = v;
1092 for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
1093 *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
1094 struct hlist_head *bucket = per_cpu_ptr(head, *cpu);
1096 if (!hlist_empty(bucket))
1097 return bucket->first;
1101 EXPORT_SYMBOL(seq_hlist_next_percpu);
1103 void __init seq_file_init(void)
1105 seq_file_cache = KMEM_CACHE(seq_file, SLAB_ACCOUNT|SLAB_PANIC);