Root/fs/seq_file.c

1/*
2 * linux/fs/seq_file.c
3 *
4 * helper functions for making synthetic files from sequences of records.
5 * initial implementation -- AV, Oct 2001.
6 */
7
8#include <linux/fs.h>
9#include <linux/module.h>
10#include <linux/seq_file.h>
11#include <linux/slab.h>
12
13#include <asm/uaccess.h>
14#include <asm/page.h>
15
16/**
17 * seq_open - initialize sequential file
18 * @file: file we initialize
19 * @op: method table describing the sequence
20 *
21 * seq_open() sets @file, associating it with a sequence described
22 * by @op. @op->start() sets the iterator up and returns the first
23 * element of sequence. @op->stop() shuts it down. @op->next()
24 * returns the next element of sequence. @op->show() prints element
25 * into the buffer. In case of error ->start() and ->next() return
26 * ERR_PTR(error). In the end of sequence they return %NULL. ->show()
27 * returns 0 in case of success and negative number in case of error.
28 * Returning SEQ_SKIP means "discard this element and move on".
29 */
30int seq_open(struct file *file, const struct seq_operations *op)
31{
32    struct seq_file *p = file->private_data;
33
34    if (!p) {
35        p = kmalloc(sizeof(*p), GFP_KERNEL);
36        if (!p)
37            return -ENOMEM;
38        file->private_data = p;
39    }
40    memset(p, 0, sizeof(*p));
41    mutex_init(&p->lock);
42    p->op = op;
43
44    /*
45     * Wrappers around seq_open(e.g. swaps_open) need to be
46     * aware of this. If they set f_version themselves, they
47     * should call seq_open first and then set f_version.
48     */
49    file->f_version = 0;
50
51    /*
52     * seq_files support lseek() and pread(). They do not implement
53     * write() at all, but we clear FMODE_PWRITE here for historical
54     * reasons.
55     *
56     * If a client of seq_files a) implements file.write() and b) wishes to
57     * support pwrite() then that client will need to implement its own
58     * file.open() which calls seq_open() and then sets FMODE_PWRITE.
59     */
60    file->f_mode &= ~FMODE_PWRITE;
61    return 0;
62}
63EXPORT_SYMBOL(seq_open);
64
65static int traverse(struct seq_file *m, loff_t offset)
66{
67    loff_t pos = 0, index;
68    int error = 0;
69    void *p;
70
71    m->version = 0;
72    index = 0;
73    m->count = m->from = 0;
74    if (!offset) {
75        m->index = index;
76        return 0;
77    }
78    if (!m->buf) {
79        m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
80        if (!m->buf)
81            return -ENOMEM;
82    }
83    p = m->op->start(m, &index);
84    while (p) {
85        error = PTR_ERR(p);
86        if (IS_ERR(p))
87            break;
88        error = m->op->show(m, p);
89        if (error < 0)
90            break;
91        if (unlikely(error)) {
92            error = 0;
93            m->count = 0;
94        }
95        if (m->count == m->size)
96            goto Eoverflow;
97        if (pos + m->count > offset) {
98            m->from = offset - pos;
99            m->count -= m->from;
100            m->index = index;
101            break;
102        }
103        pos += m->count;
104        m->count = 0;
105        if (pos == offset) {
106            index++;
107            m->index = index;
108            break;
109        }
110        p = m->op->next(m, p, &index);
111    }
112    m->op->stop(m, p);
113    m->index = index;
114    return error;
115
116Eoverflow:
117    m->op->stop(m, p);
118    kfree(m->buf);
119    m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
120    return !m->buf ? -ENOMEM : -EAGAIN;
121}
122
123/**
124 * seq_read - ->read() method for sequential files.
125 * @file: the file to read from
126 * @buf: the buffer to read to
127 * @size: the maximum number of bytes to read
128 * @ppos: the current position in the file
129 *
130 * Ready-made ->f_op->read()
131 */
132ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
133{
134    struct seq_file *m = (struct seq_file *)file->private_data;
135    size_t copied = 0;
136    loff_t pos;
137    size_t n;
138    void *p;
139    int err = 0;
140
141    mutex_lock(&m->lock);
142
143    /* Don't assume *ppos is where we left it */
144    if (unlikely(*ppos != m->read_pos)) {
145        m->read_pos = *ppos;
146        while ((err = traverse(m, *ppos)) == -EAGAIN)
147            ;
148        if (err) {
149            /* With prejudice... */
150            m->read_pos = 0;
151            m->version = 0;
152            m->index = 0;
153            m->count = 0;
154            goto Done;
155        }
156    }
157
158    /*
159     * seq_file->op->..m_start/m_stop/m_next may do special actions
160     * or optimisations based on the file->f_version, so we want to
161     * pass the file->f_version to those methods.
162     *
163     * seq_file->version is just copy of f_version, and seq_file
164     * methods can treat it simply as file version.
165     * It is copied in first and copied out after all operations.
166     * It is convenient to have it as part of structure to avoid the
167     * need of passing another argument to all the seq_file methods.
168     */
169    m->version = file->f_version;
170    /* grab buffer if we didn't have one */
171    if (!m->buf) {
172        m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
173        if (!m->buf)
174            goto Enomem;
175    }
176    /* if not empty - flush it first */
177    if (m->count) {
178        n = min(m->count, size);
179        err = copy_to_user(buf, m->buf + m->from, n);
180        if (err)
181            goto Efault;
182        m->count -= n;
183        m->from += n;
184        size -= n;
185        buf += n;
186        copied += n;
187        if (!m->count)
188            m->index++;
189        if (!size)
190            goto Done;
191    }
192    /* we need at least one record in buffer */
193    pos = m->index;
194    p = m->op->start(m, &pos);
195    while (1) {
196        err = PTR_ERR(p);
197        if (!p || IS_ERR(p))
198            break;
199        err = m->op->show(m, p);
200        if (err < 0)
201            break;
202        if (unlikely(err))
203            m->count = 0;
204        if (unlikely(!m->count)) {
205            p = m->op->next(m, p, &pos);
206            m->index = pos;
207            continue;
208        }
209        if (m->count < m->size)
210            goto Fill;
211        m->op->stop(m, p);
212        kfree(m->buf);
213        m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
214        if (!m->buf)
215            goto Enomem;
216        m->count = 0;
217        m->version = 0;
218        pos = m->index;
219        p = m->op->start(m, &pos);
220    }
221    m->op->stop(m, p);
222    m->count = 0;
223    goto Done;
224Fill:
225    /* they want more? let's try to get some more */
226    while (m->count < size) {
227        size_t offs = m->count;
228        loff_t next = pos;
229        p = m->op->next(m, p, &next);
230        if (!p || IS_ERR(p)) {
231            err = PTR_ERR(p);
232            break;
233        }
234        err = m->op->show(m, p);
235        if (m->count == m->size || err) {
236            m->count = offs;
237            if (likely(err <= 0))
238                break;
239        }
240        pos = next;
241    }
242    m->op->stop(m, p);
243    n = min(m->count, size);
244    err = copy_to_user(buf, m->buf, n);
245    if (err)
246        goto Efault;
247    copied += n;
248    m->count -= n;
249    if (m->count)
250        m->from = n;
251    else
252        pos++;
253    m->index = pos;
254Done:
255    if (!copied)
256        copied = err;
257    else {
258        *ppos += copied;
259        m->read_pos += copied;
260    }
261    file->f_version = m->version;
262    mutex_unlock(&m->lock);
263    return copied;
264Enomem:
265    err = -ENOMEM;
266    goto Done;
267Efault:
268    err = -EFAULT;
269    goto Done;
270}
271EXPORT_SYMBOL(seq_read);
272
273/**
274 * seq_lseek - ->llseek() method for sequential files.
275 * @file: the file in question
276 * @offset: new position
277 * @origin: 0 for absolute, 1 for relative position
278 *
279 * Ready-made ->f_op->llseek()
280 */
281loff_t seq_lseek(struct file *file, loff_t offset, int origin)
282{
283    struct seq_file *m = (struct seq_file *)file->private_data;
284    loff_t retval = -EINVAL;
285
286    mutex_lock(&m->lock);
287    m->version = file->f_version;
288    switch (origin) {
289        case 1:
290            offset += file->f_pos;
291        case 0:
292            if (offset < 0)
293                break;
294            retval = offset;
295            if (offset != m->read_pos) {
296                while ((retval=traverse(m, offset)) == -EAGAIN)
297                    ;
298                if (retval) {
299                    /* with extreme prejudice... */
300                    file->f_pos = 0;
301                    m->read_pos = 0;
302                    m->version = 0;
303                    m->index = 0;
304                    m->count = 0;
305                } else {
306                    m->read_pos = offset;
307                    retval = file->f_pos = offset;
308                }
309            }
310    }
311    file->f_version = m->version;
312    mutex_unlock(&m->lock);
313    return retval;
314}
315EXPORT_SYMBOL(seq_lseek);
316
317/**
318 * seq_release - free the structures associated with sequential file.
319 * @file: file in question
320 * @inode: file->f_path.dentry->d_inode
321 *
322 * Frees the structures associated with sequential file; can be used
323 * as ->f_op->release() if you don't have private data to destroy.
324 */
325int seq_release(struct inode *inode, struct file *file)
326{
327    struct seq_file *m = (struct seq_file *)file->private_data;
328    kfree(m->buf);
329    kfree(m);
330    return 0;
331}
332EXPORT_SYMBOL(seq_release);
333
334/**
335 * seq_escape - print string into buffer, escaping some characters
336 * @m: target buffer
337 * @s: string
338 * @esc: set of characters that need escaping
339 *
340 * Puts string into buffer, replacing each occurrence of character from
341 * @esc with usual octal escape. Returns 0 in case of success, -1 - in
342 * case of overflow.
343 */
344int seq_escape(struct seq_file *m, const char *s, const char *esc)
345{
346    char *end = m->buf + m->size;
347        char *p;
348    char c;
349
350        for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
351        if (!strchr(esc, c)) {
352            *p++ = c;
353            continue;
354        }
355        if (p + 3 < end) {
356            *p++ = '\\';
357            *p++ = '0' + ((c & 0300) >> 6);
358            *p++ = '0' + ((c & 070) >> 3);
359            *p++ = '0' + (c & 07);
360            continue;
361        }
362        m->count = m->size;
363        return -1;
364        }
365    m->count = p - m->buf;
366        return 0;
367}
368EXPORT_SYMBOL(seq_escape);
369
370int seq_printf(struct seq_file *m, const char *f, ...)
371{
372    va_list args;
373    int len;
374
375    if (m->count < m->size) {
376        va_start(args, f);
377        len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
378        va_end(args);
379        if (m->count + len < m->size) {
380            m->count += len;
381            return 0;
382        }
383    }
384    m->count = m->size;
385    return -1;
386}
387EXPORT_SYMBOL(seq_printf);
388
389/**
390 * mangle_path - mangle and copy path to buffer beginning
391 * @s: buffer start
392 * @p: beginning of path in above buffer
393 * @esc: set of characters that need escaping
394 *
395 * Copy the path from @p to @s, replacing each occurrence of character from
396 * @esc with usual octal escape.
397 * Returns pointer past last written character in @s, or NULL in case of
398 * failure.
399 */
400char *mangle_path(char *s, char *p, char *esc)
401{
402    while (s <= p) {
403        char c = *p++;
404        if (!c) {
405            return s;
406        } else if (!strchr(esc, c)) {
407            *s++ = c;
408        } else if (s + 4 > p) {
409            break;
410        } else {
411            *s++ = '\\';
412            *s++ = '0' + ((c & 0300) >> 6);
413            *s++ = '0' + ((c & 070) >> 3);
414            *s++ = '0' + (c & 07);
415        }
416    }
417    return NULL;
418}
419EXPORT_SYMBOL(mangle_path);
420
421/**
422 * seq_path - seq_file interface to print a pathname
423 * @m: the seq_file handle
424 * @path: the struct path to print
425 * @esc: set of characters to escape in the output
426 *
427 * return the absolute path of 'path', as represented by the
428 * dentry / mnt pair in the path parameter.
429 */
430int seq_path(struct seq_file *m, struct path *path, char *esc)
431{
432    char *buf;
433    size_t size = seq_get_buf(m, &buf);
434    int res = -1;
435
436    if (size) {
437        char *p = d_path(path, buf, size);
438        if (!IS_ERR(p)) {
439            char *end = mangle_path(buf, p, esc);
440            if (end)
441                res = end - buf;
442        }
443    }
444    seq_commit(m, res);
445
446    return res;
447}
448EXPORT_SYMBOL(seq_path);
449
450/*
451 * Same as seq_path, but relative to supplied root.
452 *
453 * root may be changed, see __d_path().
454 */
455int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
456          char *esc)
457{
458    char *buf;
459    size_t size = seq_get_buf(m, &buf);
460    int res = -ENAMETOOLONG;
461
462    if (size) {
463        char *p;
464
465        spin_lock(&dcache_lock);
466        p = __d_path(path, root, buf, size);
467        spin_unlock(&dcache_lock);
468        res = PTR_ERR(p);
469        if (!IS_ERR(p)) {
470            char *end = mangle_path(buf, p, esc);
471            if (end)
472                res = end - buf;
473            else
474                res = -ENAMETOOLONG;
475        }
476    }
477    seq_commit(m, res);
478
479    return res < 0 ? res : 0;
480}
481
482/*
483 * returns the path of the 'dentry' from the root of its filesystem.
484 */
485int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
486{
487    char *buf;
488    size_t size = seq_get_buf(m, &buf);
489    int res = -1;
490
491    if (size) {
492        char *p = dentry_path(dentry, buf, size);
493        if (!IS_ERR(p)) {
494            char *end = mangle_path(buf, p, esc);
495            if (end)
496                res = end - buf;
497        }
498    }
499    seq_commit(m, res);
500
501    return res;
502}
503
504int seq_bitmap(struct seq_file *m, const unsigned long *bits,
505                   unsigned int nr_bits)
506{
507    if (m->count < m->size) {
508        int len = bitmap_scnprintf(m->buf + m->count,
509                m->size - m->count, bits, nr_bits);
510        if (m->count + len < m->size) {
511            m->count += len;
512            return 0;
513        }
514    }
515    m->count = m->size;
516    return -1;
517}
518EXPORT_SYMBOL(seq_bitmap);
519
520int seq_bitmap_list(struct seq_file *m, const unsigned long *bits,
521        unsigned int nr_bits)
522{
523    if (m->count < m->size) {
524        int len = bitmap_scnlistprintf(m->buf + m->count,
525                m->size - m->count, bits, nr_bits);
526        if (m->count + len < m->size) {
527            m->count += len;
528            return 0;
529        }
530    }
531    m->count = m->size;
532    return -1;
533}
534EXPORT_SYMBOL(seq_bitmap_list);
535
536static void *single_start(struct seq_file *p, loff_t *pos)
537{
538    return NULL + (*pos == 0);
539}
540
541static void *single_next(struct seq_file *p, void *v, loff_t *pos)
542{
543    ++*pos;
544    return NULL;
545}
546
547static void single_stop(struct seq_file *p, void *v)
548{
549}
550
551int single_open(struct file *file, int (*show)(struct seq_file *, void *),
552        void *data)
553{
554    struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
555    int res = -ENOMEM;
556
557    if (op) {
558        op->start = single_start;
559        op->next = single_next;
560        op->stop = single_stop;
561        op->show = show;
562        res = seq_open(file, op);
563        if (!res)
564            ((struct seq_file *)file->private_data)->private = data;
565        else
566            kfree(op);
567    }
568    return res;
569}
570EXPORT_SYMBOL(single_open);
571
572int single_release(struct inode *inode, struct file *file)
573{
574    const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
575    int res = seq_release(inode, file);
576    kfree(op);
577    return res;
578}
579EXPORT_SYMBOL(single_release);
580
581int seq_release_private(struct inode *inode, struct file *file)
582{
583    struct seq_file *seq = file->private_data;
584
585    kfree(seq->private);
586    seq->private = NULL;
587    return seq_release(inode, file);
588}
589EXPORT_SYMBOL(seq_release_private);
590
591void *__seq_open_private(struct file *f, const struct seq_operations *ops,
592        int psize)
593{
594    int rc;
595    void *private;
596    struct seq_file *seq;
597
598    private = kzalloc(psize, GFP_KERNEL);
599    if (private == NULL)
600        goto out;
601
602    rc = seq_open(f, ops);
603    if (rc < 0)
604        goto out_free;
605
606    seq = f->private_data;
607    seq->private = private;
608    return private;
609
610out_free:
611    kfree(private);
612out:
613    return NULL;
614}
615EXPORT_SYMBOL(__seq_open_private);
616
617int seq_open_private(struct file *filp, const struct seq_operations *ops,
618        int psize)
619{
620    return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
621}
622EXPORT_SYMBOL(seq_open_private);
623
624int seq_putc(struct seq_file *m, char c)
625{
626    if (m->count < m->size) {
627        m->buf[m->count++] = c;
628        return 0;
629    }
630    return -1;
631}
632EXPORT_SYMBOL(seq_putc);
633
634int seq_puts(struct seq_file *m, const char *s)
635{
636    int len = strlen(s);
637    if (m->count + len < m->size) {
638        memcpy(m->buf + m->count, s, len);
639        m->count += len;
640        return 0;
641    }
642    m->count = m->size;
643    return -1;
644}
645EXPORT_SYMBOL(seq_puts);
646
647/**
648 * seq_write - write arbitrary data to buffer
649 * @seq: seq_file identifying the buffer to which data should be written
650 * @data: data address
651 * @len: number of bytes
652 *
653 * Return 0 on success, non-zero otherwise.
654 */
655int seq_write(struct seq_file *seq, const void *data, size_t len)
656{
657    if (seq->count + len < seq->size) {
658        memcpy(seq->buf + seq->count, data, len);
659        seq->count += len;
660        return 0;
661    }
662    seq->count = seq->size;
663    return -1;
664}
665EXPORT_SYMBOL(seq_write);
666
667struct list_head *seq_list_start(struct list_head *head, loff_t pos)
668{
669    struct list_head *lh;
670
671    list_for_each(lh, head)
672        if (pos-- == 0)
673            return lh;
674
675    return NULL;
676}
677EXPORT_SYMBOL(seq_list_start);
678
679struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
680{
681    if (!pos)
682        return head;
683
684    return seq_list_start(head, pos - 1);
685}
686EXPORT_SYMBOL(seq_list_start_head);
687
688struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
689{
690    struct list_head *lh;
691
692    lh = ((struct list_head *)v)->next;
693    ++*ppos;
694    return lh == head ? NULL : lh;
695}
696EXPORT_SYMBOL(seq_list_next);
697
698/**
699 * seq_hlist_start - start an iteration of a hlist
700 * @head: the head of the hlist
701 * @pos: the start position of the sequence
702 *
703 * Called at seq_file->op->start().
704 */
705struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
706{
707    struct hlist_node *node;
708
709    hlist_for_each(node, head)
710        if (pos-- == 0)
711            return node;
712    return NULL;
713}
714EXPORT_SYMBOL(seq_hlist_start);
715
716/**
717 * seq_hlist_start_head - start an iteration of a hlist
718 * @head: the head of the hlist
719 * @pos: the start position of the sequence
720 *
721 * Called at seq_file->op->start(). Call this function if you want to
722 * print a header at the top of the output.
723 */
724struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
725{
726    if (!pos)
727        return SEQ_START_TOKEN;
728
729    return seq_hlist_start(head, pos - 1);
730}
731EXPORT_SYMBOL(seq_hlist_start_head);
732
733/**
734 * seq_hlist_next - move to the next position of the hlist
735 * @v: the current iterator
736 * @head: the head of the hlist
737 * @ppos: the current position
738 *
739 * Called at seq_file->op->next().
740 */
741struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
742                  loff_t *ppos)
743{
744    struct hlist_node *node = v;
745
746    ++*ppos;
747    if (v == SEQ_START_TOKEN)
748        return head->first;
749    else
750        return node->next;
751}
752EXPORT_SYMBOL(seq_hlist_next);
753
754/**
755 * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
756 * @head: the head of the hlist
757 * @pos: the start position of the sequence
758 *
759 * Called at seq_file->op->start().
760 *
761 * This list-traversal primitive may safely run concurrently with
762 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
763 * as long as the traversal is guarded by rcu_read_lock().
764 */
765struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
766                       loff_t pos)
767{
768    struct hlist_node *node;
769
770    __hlist_for_each_rcu(node, head)
771        if (pos-- == 0)
772            return node;
773    return NULL;
774}
775EXPORT_SYMBOL(seq_hlist_start_rcu);
776
777/**
778 * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
779 * @head: the head of the hlist
780 * @pos: the start position of the sequence
781 *
782 * Called at seq_file->op->start(). Call this function if you want to
783 * print a header at the top of the output.
784 *
785 * This list-traversal primitive may safely run concurrently with
786 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
787 * as long as the traversal is guarded by rcu_read_lock().
788 */
789struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
790                        loff_t pos)
791{
792    if (!pos)
793        return SEQ_START_TOKEN;
794
795    return seq_hlist_start_rcu(head, pos - 1);
796}
797EXPORT_SYMBOL(seq_hlist_start_head_rcu);
798
799/**
800 * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
801 * @v: the current iterator
802 * @head: the head of the hlist
803 * @ppos: the current position
804 *
805 * Called at seq_file->op->next().
806 *
807 * This list-traversal primitive may safely run concurrently with
808 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
809 * as long as the traversal is guarded by rcu_read_lock().
810 */
811struct hlist_node *seq_hlist_next_rcu(void *v,
812                      struct hlist_head *head,
813                      loff_t *ppos)
814{
815    struct hlist_node *node = v;
816
817    ++*ppos;
818    if (v == SEQ_START_TOKEN)
819        return rcu_dereference(head->first);
820    else
821        return rcu_dereference(node->next);
822}
823EXPORT_SYMBOL(seq_hlist_next_rcu);
824

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