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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/sysfs/file.c - sysfs regular (text) file implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8 *
9 * Please see Documentation/filesystems/sysfs.rst for more information.
10 */
11
12#include <linux/module.h>
13#include <linux/kobject.h>
14#include <linux/slab.h>
15#include <linux/list.h>
16#include <linux/mutex.h>
17#include <linux/seq_file.h>
18#include <linux/mm.h>
19
20#include "sysfs.h"
21
22/*
23 * Determine ktype->sysfs_ops for the given kernfs_node. This function
24 * must be called while holding an active reference.
25 */
26static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
27{
28 struct kobject *kobj = kn->parent->priv;
29
30 if (kn->flags & KERNFS_LOCKDEP)
31 lockdep_assert_held(kn);
32 return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
33}
34
35/*
36 * Reads on sysfs are handled through seq_file, which takes care of hairy
37 * details like buffering and seeking. The following function pipes
38 * sysfs_ops->show() result through seq_file.
39 */
40static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
41{
42 struct kernfs_open_file *of = sf->private;
43 struct kobject *kobj = of->kn->parent->priv;
44 const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
45 ssize_t count;
46 char *buf;
47
48 if (WARN_ON_ONCE(!ops->show))
49 return -EINVAL;
50
51 /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
52 count = seq_get_buf(sf, &buf);
53 if (count < PAGE_SIZE) {
54 seq_commit(sf, -1);
55 return 0;
56 }
57 memset(buf, 0, PAGE_SIZE);
58
59 count = ops->show(kobj, of->kn->priv, buf);
60 if (count < 0)
61 return count;
62
63 /*
64 * The code works fine with PAGE_SIZE return but it's likely to
65 * indicate truncated result or overflow in normal use cases.
66 */
67 if (count >= (ssize_t)PAGE_SIZE) {
68 printk("fill_read_buffer: %pS returned bad count\n",
69 ops->show);
70 /* Try to struggle along */
71 count = PAGE_SIZE - 1;
72 }
73 seq_commit(sf, count);
74 return 0;
75}
76
77static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
78 size_t count, loff_t pos)
79{
80 struct bin_attribute *battr = of->kn->priv;
81 struct kobject *kobj = of->kn->parent->priv;
82 loff_t size = file_inode(of->file)->i_size;
83
84 if (!count)
85 return 0;
86
87 if (size) {
88 if (pos >= size)
89 return 0;
90 if (pos + count > size)
91 count = size - pos;
92 }
93
94 if (!battr->read)
95 return -EIO;
96
97 return battr->read(of->file, kobj, battr, buf, pos, count);
98}
99
100/* kernfs read callback for regular sysfs files with pre-alloc */
101static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
102 size_t count, loff_t pos)
103{
104 const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
105 struct kobject *kobj = of->kn->parent->priv;
106 ssize_t len;
107
108 /*
109 * If buf != of->prealloc_buf, we don't know how
110 * large it is, so cannot safely pass it to ->show
111 */
112 if (WARN_ON_ONCE(buf != of->prealloc_buf))
113 return 0;
114 len = ops->show(kobj, of->kn->priv, buf);
115 if (len < 0)
116 return len;
117 if (pos) {
118 if (len <= pos)
119 return 0;
120 len -= pos;
121 memmove(buf, buf + pos, len);
122 }
123 return min_t(ssize_t, count, len);
124}
125
126/* kernfs write callback for regular sysfs files */
127static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
128 size_t count, loff_t pos)
129{
130 const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
131 struct kobject *kobj = of->kn->parent->priv;
132
133 if (!count)
134 return 0;
135
136 return ops->store(kobj, of->kn->priv, buf, count);
137}
138
139/* kernfs write callback for bin sysfs files */
140static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
141 size_t count, loff_t pos)
142{
143 struct bin_attribute *battr = of->kn->priv;
144 struct kobject *kobj = of->kn->parent->priv;
145 loff_t size = file_inode(of->file)->i_size;
146
147 if (size) {
148 if (size <= pos)
149 return -EFBIG;
150 count = min_t(ssize_t, count, size - pos);
151 }
152 if (!count)
153 return 0;
154
155 if (!battr->write)
156 return -EIO;
157
158 return battr->write(of->file, kobj, battr, buf, pos, count);
159}
160
161static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
162 struct vm_area_struct *vma)
163{
164 struct bin_attribute *battr = of->kn->priv;
165 struct kobject *kobj = of->kn->parent->priv;
166
167 return battr->mmap(of->file, kobj, battr, vma);
168}
169
170static loff_t sysfs_kf_bin_llseek(struct kernfs_open_file *of, loff_t offset,
171 int whence)
172{
173 struct bin_attribute *battr = of->kn->priv;
174 struct kobject *kobj = of->kn->parent->priv;
175
176 if (battr->llseek)
177 return battr->llseek(of->file, kobj, battr, offset, whence);
178 else
179 return generic_file_llseek(of->file, offset, whence);
180}
181
182static int sysfs_kf_bin_open(struct kernfs_open_file *of)
183{
184 struct bin_attribute *battr = of->kn->priv;
185
186 if (battr->f_mapping)
187 of->file->f_mapping = battr->f_mapping();
188
189 return 0;
190}
191
192void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
193{
194 struct kernfs_node *kn = kobj->sd, *tmp;
195
196 if (kn && dir)
197 kn = kernfs_find_and_get(kn, dir);
198 else
199 kernfs_get(kn);
200
201 if (kn && attr) {
202 tmp = kernfs_find_and_get(kn, attr);
203 kernfs_put(kn);
204 kn = tmp;
205 }
206
207 if (kn) {
208 kernfs_notify(kn);
209 kernfs_put(kn);
210 }
211}
212EXPORT_SYMBOL_GPL(sysfs_notify);
213
214static const struct kernfs_ops sysfs_file_kfops_empty = {
215};
216
217static const struct kernfs_ops sysfs_file_kfops_ro = {
218 .seq_show = sysfs_kf_seq_show,
219};
220
221static const struct kernfs_ops sysfs_file_kfops_wo = {
222 .write = sysfs_kf_write,
223};
224
225static const struct kernfs_ops sysfs_file_kfops_rw = {
226 .seq_show = sysfs_kf_seq_show,
227 .write = sysfs_kf_write,
228};
229
230static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
231 .read = sysfs_kf_read,
232 .prealloc = true,
233};
234
235static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
236 .write = sysfs_kf_write,
237 .prealloc = true,
238};
239
240static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
241 .read = sysfs_kf_read,
242 .write = sysfs_kf_write,
243 .prealloc = true,
244};
245
246static const struct kernfs_ops sysfs_bin_kfops_ro = {
247 .read = sysfs_kf_bin_read,
248};
249
250static const struct kernfs_ops sysfs_bin_kfops_wo = {
251 .write = sysfs_kf_bin_write,
252};
253
254static const struct kernfs_ops sysfs_bin_kfops_rw = {
255 .read = sysfs_kf_bin_read,
256 .write = sysfs_kf_bin_write,
257};
258
259static const struct kernfs_ops sysfs_bin_kfops_mmap = {
260 .read = sysfs_kf_bin_read,
261 .write = sysfs_kf_bin_write,
262 .mmap = sysfs_kf_bin_mmap,
263 .open = sysfs_kf_bin_open,
264 .llseek = sysfs_kf_bin_llseek,
265};
266
267int sysfs_add_file_mode_ns(struct kernfs_node *parent,
268 const struct attribute *attr, umode_t mode, kuid_t uid,
269 kgid_t gid, const void *ns)
270{
271 struct kobject *kobj = parent->priv;
272 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
273 struct lock_class_key *key = NULL;
274 const struct kernfs_ops *ops = NULL;
275 struct kernfs_node *kn;
276
277 /* every kobject with an attribute needs a ktype assigned */
278 if (WARN(!sysfs_ops, KERN_ERR
279 "missing sysfs attribute operations for kobject: %s\n",
280 kobject_name(kobj)))
281 return -EINVAL;
282
283 if (mode & SYSFS_PREALLOC) {
284 if (sysfs_ops->show && sysfs_ops->store)
285 ops = &sysfs_prealloc_kfops_rw;
286 else if (sysfs_ops->show)
287 ops = &sysfs_prealloc_kfops_ro;
288 else if (sysfs_ops->store)
289 ops = &sysfs_prealloc_kfops_wo;
290 } else {
291 if (sysfs_ops->show && sysfs_ops->store)
292 ops = &sysfs_file_kfops_rw;
293 else if (sysfs_ops->show)
294 ops = &sysfs_file_kfops_ro;
295 else if (sysfs_ops->store)
296 ops = &sysfs_file_kfops_wo;
297 }
298
299 if (!ops)
300 ops = &sysfs_file_kfops_empty;
301
302#ifdef CONFIG_DEBUG_LOCK_ALLOC
303 if (!attr->ignore_lockdep)
304 key = attr->key ?: (struct lock_class_key *)&attr->skey;
305#endif
306
307 kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
308 PAGE_SIZE, ops, (void *)attr, ns, key);
309 if (IS_ERR(kn)) {
310 if (PTR_ERR(kn) == -EEXIST)
311 sysfs_warn_dup(parent, attr->name);
312 return PTR_ERR(kn);
313 }
314 return 0;
315}
316
317int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
318 const struct bin_attribute *battr, umode_t mode,
319 kuid_t uid, kgid_t gid, const void *ns)
320{
321 const struct attribute *attr = &battr->attr;
322 struct lock_class_key *key = NULL;
323 const struct kernfs_ops *ops;
324 struct kernfs_node *kn;
325
326 if (battr->mmap)
327 ops = &sysfs_bin_kfops_mmap;
328 else if (battr->read && battr->write)
329 ops = &sysfs_bin_kfops_rw;
330 else if (battr->read)
331 ops = &sysfs_bin_kfops_ro;
332 else if (battr->write)
333 ops = &sysfs_bin_kfops_wo;
334 else
335 ops = &sysfs_file_kfops_empty;
336
337#ifdef CONFIG_DEBUG_LOCK_ALLOC
338 if (!attr->ignore_lockdep)
339 key = attr->key ?: (struct lock_class_key *)&attr->skey;
340#endif
341
342 kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
343 battr->size, ops, (void *)attr, ns, key);
344 if (IS_ERR(kn)) {
345 if (PTR_ERR(kn) == -EEXIST)
346 sysfs_warn_dup(parent, attr->name);
347 return PTR_ERR(kn);
348 }
349 return 0;
350}
351
352/**
353 * sysfs_create_file_ns - create an attribute file for an object with custom ns
354 * @kobj: object we're creating for
355 * @attr: attribute descriptor
356 * @ns: namespace the new file should belong to
357 */
358int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
359 const void *ns)
360{
361 kuid_t uid;
362 kgid_t gid;
363
364 if (WARN_ON(!kobj || !kobj->sd || !attr))
365 return -EINVAL;
366
367 kobject_get_ownership(kobj, &uid, &gid);
368 return sysfs_add_file_mode_ns(kobj->sd, attr, attr->mode, uid, gid, ns);
369}
370EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
371
372int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
373{
374 int err = 0;
375 int i;
376
377 for (i = 0; ptr[i] && !err; i++)
378 err = sysfs_create_file(kobj, ptr[i]);
379 if (err)
380 while (--i >= 0)
381 sysfs_remove_file(kobj, ptr[i]);
382 return err;
383}
384EXPORT_SYMBOL_GPL(sysfs_create_files);
385
386/**
387 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
388 * @kobj: object we're acting for.
389 * @attr: attribute descriptor.
390 * @group: group name.
391 */
392int sysfs_add_file_to_group(struct kobject *kobj,
393 const struct attribute *attr, const char *group)
394{
395 struct kernfs_node *parent;
396 kuid_t uid;
397 kgid_t gid;
398 int error;
399
400 if (group) {
401 parent = kernfs_find_and_get(kobj->sd, group);
402 } else {
403 parent = kobj->sd;
404 kernfs_get(parent);
405 }
406
407 if (!parent)
408 return -ENOENT;
409
410 kobject_get_ownership(kobj, &uid, &gid);
411 error = sysfs_add_file_mode_ns(parent, attr, attr->mode, uid, gid,
412 NULL);
413 kernfs_put(parent);
414
415 return error;
416}
417EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
418
419/**
420 * sysfs_chmod_file - update the modified mode value on an object attribute.
421 * @kobj: object we're acting for.
422 * @attr: attribute descriptor.
423 * @mode: file permissions.
424 *
425 */
426int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
427 umode_t mode)
428{
429 struct kernfs_node *kn;
430 struct iattr newattrs;
431 int rc;
432
433 kn = kernfs_find_and_get(kobj->sd, attr->name);
434 if (!kn)
435 return -ENOENT;
436
437 newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
438 newattrs.ia_valid = ATTR_MODE;
439
440 rc = kernfs_setattr(kn, &newattrs);
441
442 kernfs_put(kn);
443 return rc;
444}
445EXPORT_SYMBOL_GPL(sysfs_chmod_file);
446
447/**
448 * sysfs_break_active_protection - break "active" protection
449 * @kobj: The kernel object @attr is associated with.
450 * @attr: The attribute to break the "active" protection for.
451 *
452 * With sysfs, just like kernfs, deletion of an attribute is postponed until
453 * all active .show() and .store() callbacks have finished unless this function
454 * is called. Hence this function is useful in methods that implement self
455 * deletion.
456 */
457struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
458 const struct attribute *attr)
459{
460 struct kernfs_node *kn;
461
462 kobject_get(kobj);
463 kn = kernfs_find_and_get(kobj->sd, attr->name);
464 if (kn)
465 kernfs_break_active_protection(kn);
466 return kn;
467}
468EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
469
470/**
471 * sysfs_unbreak_active_protection - restore "active" protection
472 * @kn: Pointer returned by sysfs_break_active_protection().
473 *
474 * Undo the effects of sysfs_break_active_protection(). Since this function
475 * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
476 * argument passed to sysfs_break_active_protection() that attribute may have
477 * been removed between the sysfs_break_active_protection() and
478 * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
479 * this function has returned.
480 */
481void sysfs_unbreak_active_protection(struct kernfs_node *kn)
482{
483 struct kobject *kobj = kn->parent->priv;
484
485 kernfs_unbreak_active_protection(kn);
486 kernfs_put(kn);
487 kobject_put(kobj);
488}
489EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
490
491/**
492 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
493 * @kobj: object we're acting for
494 * @attr: attribute descriptor
495 * @ns: namespace tag of the file to remove
496 *
497 * Hash the attribute name and namespace tag and kill the victim.
498 */
499void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
500 const void *ns)
501{
502 struct kernfs_node *parent = kobj->sd;
503
504 kernfs_remove_by_name_ns(parent, attr->name, ns);
505}
506EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
507
508/**
509 * sysfs_remove_file_self - remove an object attribute from its own method
510 * @kobj: object we're acting for
511 * @attr: attribute descriptor
512 *
513 * See kernfs_remove_self() for details.
514 */
515bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
516{
517 struct kernfs_node *parent = kobj->sd;
518 struct kernfs_node *kn;
519 bool ret;
520
521 kn = kernfs_find_and_get(parent, attr->name);
522 if (WARN_ON_ONCE(!kn))
523 return false;
524
525 ret = kernfs_remove_self(kn);
526
527 kernfs_put(kn);
528 return ret;
529}
530EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
531
532void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
533{
534 int i;
535
536 for (i = 0; ptr[i]; i++)
537 sysfs_remove_file(kobj, ptr[i]);
538}
539EXPORT_SYMBOL_GPL(sysfs_remove_files);
540
541/**
542 * sysfs_remove_file_from_group - remove an attribute file from a group.
543 * @kobj: object we're acting for.
544 * @attr: attribute descriptor.
545 * @group: group name.
546 */
547void sysfs_remove_file_from_group(struct kobject *kobj,
548 const struct attribute *attr, const char *group)
549{
550 struct kernfs_node *parent;
551
552 if (group) {
553 parent = kernfs_find_and_get(kobj->sd, group);
554 } else {
555 parent = kobj->sd;
556 kernfs_get(parent);
557 }
558
559 if (parent) {
560 kernfs_remove_by_name(parent, attr->name);
561 kernfs_put(parent);
562 }
563}
564EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
565
566/**
567 * sysfs_create_bin_file - create binary file for object.
568 * @kobj: object.
569 * @attr: attribute descriptor.
570 */
571int sysfs_create_bin_file(struct kobject *kobj,
572 const struct bin_attribute *attr)
573{
574 kuid_t uid;
575 kgid_t gid;
576
577 if (WARN_ON(!kobj || !kobj->sd || !attr))
578 return -EINVAL;
579
580 kobject_get_ownership(kobj, &uid, &gid);
581 return sysfs_add_bin_file_mode_ns(kobj->sd, attr, attr->attr.mode, uid,
582 gid, NULL);
583}
584EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
585
586/**
587 * sysfs_remove_bin_file - remove binary file for object.
588 * @kobj: object.
589 * @attr: attribute descriptor.
590 */
591void sysfs_remove_bin_file(struct kobject *kobj,
592 const struct bin_attribute *attr)
593{
594 kernfs_remove_by_name(kobj->sd, attr->attr.name);
595}
596EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
597
598static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
599 kgid_t kgid)
600{
601 struct iattr newattrs = {
602 .ia_valid = ATTR_UID | ATTR_GID,
603 .ia_uid = kuid,
604 .ia_gid = kgid,
605 };
606 return kernfs_setattr(kn, &newattrs);
607}
608
609/**
610 * sysfs_link_change_owner - change owner of a sysfs file.
611 * @kobj: object of the kernfs_node the symlink is located in.
612 * @targ: object of the kernfs_node the symlink points to.
613 * @name: name of the link.
614 * @kuid: new owner's kuid
615 * @kgid: new owner's kgid
616 *
617 * This function looks up the sysfs symlink entry @name under @kobj and changes
618 * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
619 * @targ.
620 *
621 * Returns 0 on success or error code on failure.
622 */
623int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
624 const char *name, kuid_t kuid, kgid_t kgid)
625{
626 struct kernfs_node *kn = NULL;
627 int error;
628
629 if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
630 return -EINVAL;
631
632 error = -ENOENT;
633 kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
634 if (!kn)
635 goto out;
636
637 error = -EINVAL;
638 if (kernfs_type(kn) != KERNFS_LINK)
639 goto out;
640 if (kn->symlink.target_kn->priv != targ)
641 goto out;
642
643 error = internal_change_owner(kn, kuid, kgid);
644
645out:
646 kernfs_put(kn);
647 return error;
648}
649
650/**
651 * sysfs_file_change_owner - change owner of a sysfs file.
652 * @kobj: object.
653 * @name: name of the file to change.
654 * @kuid: new owner's kuid
655 * @kgid: new owner's kgid
656 *
657 * This function looks up the sysfs entry @name under @kobj and changes the
658 * ownership to @kuid/@kgid.
659 *
660 * Returns 0 on success or error code on failure.
661 */
662int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
663 kgid_t kgid)
664{
665 struct kernfs_node *kn;
666 int error;
667
668 if (!name)
669 return -EINVAL;
670
671 if (!kobj->state_in_sysfs)
672 return -EINVAL;
673
674 kn = kernfs_find_and_get(kobj->sd, name);
675 if (!kn)
676 return -ENOENT;
677
678 error = internal_change_owner(kn, kuid, kgid);
679
680 kernfs_put(kn);
681
682 return error;
683}
684EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
685
686/**
687 * sysfs_change_owner - change owner of the given object.
688 * @kobj: object.
689 * @kuid: new owner's kuid
690 * @kgid: new owner's kgid
691 *
692 * Change the owner of the default directory, files, groups, and attributes of
693 * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
694 * entries for a kobject are added by driver core. In summary,
695 * sysfs_change_owner() takes care of the default directory entry for @kobj,
696 * the default attributes associated with the ktype of @kobj and the default
697 * attributes associated with the ktype of @kobj.
698 * Additional properties not added by driver core have to be changed by the
699 * driver or subsystem which created them. This is similar to how
700 * driver/subsystem specific entries are removed.
701 *
702 * Returns 0 on success or error code on failure.
703 */
704int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
705{
706 int error;
707 const struct kobj_type *ktype;
708
709 if (!kobj->state_in_sysfs)
710 return -EINVAL;
711
712 /* Change the owner of the kobject itself. */
713 error = internal_change_owner(kobj->sd, kuid, kgid);
714 if (error)
715 return error;
716
717 ktype = get_ktype(kobj);
718 if (ktype) {
719 /*
720 * Change owner of the default groups associated with the
721 * ktype of @kobj.
722 */
723 error = sysfs_groups_change_owner(kobj, ktype->default_groups,
724 kuid, kgid);
725 if (error)
726 return error;
727 }
728
729 return 0;
730}
731EXPORT_SYMBOL_GPL(sysfs_change_owner);
732
733/**
734 * sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
735 * @buf: start of PAGE_SIZE buffer.
736 * @fmt: format
737 * @...: optional arguments to @format
738 *
739 *
740 * Returns number of characters written to @buf.
741 */
742int sysfs_emit(char *buf, const char *fmt, ...)
743{
744 va_list args;
745 int len;
746
747 if (WARN(!buf || offset_in_page(buf),
748 "invalid sysfs_emit: buf:%p\n", buf))
749 return 0;
750
751 va_start(args, fmt);
752 len = vscnprintf(buf, PAGE_SIZE, fmt, args);
753 va_end(args);
754
755 return len;
756}
757EXPORT_SYMBOL_GPL(sysfs_emit);
758
759/**
760 * sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
761 * @buf: start of PAGE_SIZE buffer.
762 * @at: offset in @buf to start write in bytes
763 * @at must be >= 0 && < PAGE_SIZE
764 * @fmt: format
765 * @...: optional arguments to @fmt
766 *
767 *
768 * Returns number of characters written starting at &@buf[@at].
769 */
770int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
771{
772 va_list args;
773 int len;
774
775 if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
776 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
777 return 0;
778
779 va_start(args, fmt);
780 len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
781 va_end(args);
782
783 return len;
784}
785EXPORT_SYMBOL_GPL(sysfs_emit_at);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/sysfs/file.c - sysfs regular (text) file implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8 *
9 * Please see Documentation/filesystems/sysfs.rst for more information.
10 */
11
12#include <linux/module.h>
13#include <linux/kobject.h>
14#include <linux/slab.h>
15#include <linux/list.h>
16#include <linux/mutex.h>
17#include <linux/seq_file.h>
18#include <linux/mm.h>
19
20#include "sysfs.h"
21
22/*
23 * Determine ktype->sysfs_ops for the given kernfs_node. This function
24 * must be called while holding an active reference.
25 */
26static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
27{
28 struct kobject *kobj = kn->parent->priv;
29
30 if (kn->flags & KERNFS_LOCKDEP)
31 lockdep_assert_held(kn);
32 return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
33}
34
35/*
36 * Reads on sysfs are handled through seq_file, which takes care of hairy
37 * details like buffering and seeking. The following function pipes
38 * sysfs_ops->show() result through seq_file.
39 */
40static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
41{
42 struct kernfs_open_file *of = sf->private;
43 struct kobject *kobj = of->kn->parent->priv;
44 const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
45 ssize_t count;
46 char *buf;
47
48 /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
49 count = seq_get_buf(sf, &buf);
50 if (count < PAGE_SIZE) {
51 seq_commit(sf, -1);
52 return 0;
53 }
54 memset(buf, 0, PAGE_SIZE);
55
56 /*
57 * Invoke show(). Control may reach here via seq file lseek even
58 * if @ops->show() isn't implemented.
59 */
60 if (ops->show) {
61 count = ops->show(kobj, of->kn->priv, buf);
62 if (count < 0)
63 return count;
64 }
65
66 /*
67 * The code works fine with PAGE_SIZE return but it's likely to
68 * indicate truncated result or overflow in normal use cases.
69 */
70 if (count >= (ssize_t)PAGE_SIZE) {
71 printk("fill_read_buffer: %pS returned bad count\n",
72 ops->show);
73 /* Try to struggle along */
74 count = PAGE_SIZE - 1;
75 }
76 seq_commit(sf, count);
77 return 0;
78}
79
80static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
81 size_t count, loff_t pos)
82{
83 struct bin_attribute *battr = of->kn->priv;
84 struct kobject *kobj = of->kn->parent->priv;
85 loff_t size = file_inode(of->file)->i_size;
86
87 if (!count)
88 return 0;
89
90 if (size) {
91 if (pos >= size)
92 return 0;
93 if (pos + count > size)
94 count = size - pos;
95 }
96
97 if (!battr->read)
98 return -EIO;
99
100 return battr->read(of->file, kobj, battr, buf, pos, count);
101}
102
103/* kernfs read callback for regular sysfs files with pre-alloc */
104static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
105 size_t count, loff_t pos)
106{
107 const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
108 struct kobject *kobj = of->kn->parent->priv;
109 ssize_t len;
110
111 /*
112 * If buf != of->prealloc_buf, we don't know how
113 * large it is, so cannot safely pass it to ->show
114 */
115 if (WARN_ON_ONCE(buf != of->prealloc_buf))
116 return 0;
117 len = ops->show(kobj, of->kn->priv, buf);
118 if (len < 0)
119 return len;
120 if (pos) {
121 if (len <= pos)
122 return 0;
123 len -= pos;
124 memmove(buf, buf + pos, len);
125 }
126 return min_t(ssize_t, count, len);
127}
128
129/* kernfs write callback for regular sysfs files */
130static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
131 size_t count, loff_t pos)
132{
133 const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
134 struct kobject *kobj = of->kn->parent->priv;
135
136 if (!count)
137 return 0;
138
139 return ops->store(kobj, of->kn->priv, buf, count);
140}
141
142/* kernfs write callback for bin sysfs files */
143static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
144 size_t count, loff_t pos)
145{
146 struct bin_attribute *battr = of->kn->priv;
147 struct kobject *kobj = of->kn->parent->priv;
148 loff_t size = file_inode(of->file)->i_size;
149
150 if (size) {
151 if (size <= pos)
152 return -EFBIG;
153 count = min_t(ssize_t, count, size - pos);
154 }
155 if (!count)
156 return 0;
157
158 if (!battr->write)
159 return -EIO;
160
161 return battr->write(of->file, kobj, battr, buf, pos, count);
162}
163
164static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
165 struct vm_area_struct *vma)
166{
167 struct bin_attribute *battr = of->kn->priv;
168 struct kobject *kobj = of->kn->parent->priv;
169
170 return battr->mmap(of->file, kobj, battr, vma);
171}
172
173static int sysfs_kf_bin_open(struct kernfs_open_file *of)
174{
175 struct bin_attribute *battr = of->kn->priv;
176
177 if (battr->mapping)
178 of->file->f_mapping = battr->mapping;
179
180 return 0;
181}
182
183void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
184{
185 struct kernfs_node *kn = kobj->sd, *tmp;
186
187 if (kn && dir)
188 kn = kernfs_find_and_get(kn, dir);
189 else
190 kernfs_get(kn);
191
192 if (kn && attr) {
193 tmp = kernfs_find_and_get(kn, attr);
194 kernfs_put(kn);
195 kn = tmp;
196 }
197
198 if (kn) {
199 kernfs_notify(kn);
200 kernfs_put(kn);
201 }
202}
203EXPORT_SYMBOL_GPL(sysfs_notify);
204
205static const struct kernfs_ops sysfs_file_kfops_empty = {
206};
207
208static const struct kernfs_ops sysfs_file_kfops_ro = {
209 .seq_show = sysfs_kf_seq_show,
210};
211
212static const struct kernfs_ops sysfs_file_kfops_wo = {
213 .write = sysfs_kf_write,
214};
215
216static const struct kernfs_ops sysfs_file_kfops_rw = {
217 .seq_show = sysfs_kf_seq_show,
218 .write = sysfs_kf_write,
219};
220
221static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
222 .read = sysfs_kf_read,
223 .prealloc = true,
224};
225
226static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
227 .write = sysfs_kf_write,
228 .prealloc = true,
229};
230
231static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
232 .read = sysfs_kf_read,
233 .write = sysfs_kf_write,
234 .prealloc = true,
235};
236
237static const struct kernfs_ops sysfs_bin_kfops_ro = {
238 .read = sysfs_kf_bin_read,
239};
240
241static const struct kernfs_ops sysfs_bin_kfops_wo = {
242 .write = sysfs_kf_bin_write,
243};
244
245static const struct kernfs_ops sysfs_bin_kfops_rw = {
246 .read = sysfs_kf_bin_read,
247 .write = sysfs_kf_bin_write,
248};
249
250static const struct kernfs_ops sysfs_bin_kfops_mmap = {
251 .read = sysfs_kf_bin_read,
252 .write = sysfs_kf_bin_write,
253 .mmap = sysfs_kf_bin_mmap,
254 .open = sysfs_kf_bin_open,
255};
256
257int sysfs_add_file_mode_ns(struct kernfs_node *parent,
258 const struct attribute *attr, bool is_bin,
259 umode_t mode, kuid_t uid, kgid_t gid, const void *ns)
260{
261 struct lock_class_key *key = NULL;
262 const struct kernfs_ops *ops;
263 struct kernfs_node *kn;
264 loff_t size;
265
266 if (!is_bin) {
267 struct kobject *kobj = parent->priv;
268 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
269
270 /* every kobject with an attribute needs a ktype assigned */
271 if (WARN(!sysfs_ops, KERN_ERR
272 "missing sysfs attribute operations for kobject: %s\n",
273 kobject_name(kobj)))
274 return -EINVAL;
275
276 if (sysfs_ops->show && sysfs_ops->store) {
277 if (mode & SYSFS_PREALLOC)
278 ops = &sysfs_prealloc_kfops_rw;
279 else
280 ops = &sysfs_file_kfops_rw;
281 } else if (sysfs_ops->show) {
282 if (mode & SYSFS_PREALLOC)
283 ops = &sysfs_prealloc_kfops_ro;
284 else
285 ops = &sysfs_file_kfops_ro;
286 } else if (sysfs_ops->store) {
287 if (mode & SYSFS_PREALLOC)
288 ops = &sysfs_prealloc_kfops_wo;
289 else
290 ops = &sysfs_file_kfops_wo;
291 } else
292 ops = &sysfs_file_kfops_empty;
293
294 size = PAGE_SIZE;
295 } else {
296 struct bin_attribute *battr = (void *)attr;
297
298 if (battr->mmap)
299 ops = &sysfs_bin_kfops_mmap;
300 else if (battr->read && battr->write)
301 ops = &sysfs_bin_kfops_rw;
302 else if (battr->read)
303 ops = &sysfs_bin_kfops_ro;
304 else if (battr->write)
305 ops = &sysfs_bin_kfops_wo;
306 else
307 ops = &sysfs_file_kfops_empty;
308
309 size = battr->size;
310 }
311
312#ifdef CONFIG_DEBUG_LOCK_ALLOC
313 if (!attr->ignore_lockdep)
314 key = attr->key ?: (struct lock_class_key *)&attr->skey;
315#endif
316
317 kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
318 size, ops, (void *)attr, ns, key);
319 if (IS_ERR(kn)) {
320 if (PTR_ERR(kn) == -EEXIST)
321 sysfs_warn_dup(parent, attr->name);
322 return PTR_ERR(kn);
323 }
324 return 0;
325}
326
327/**
328 * sysfs_create_file_ns - create an attribute file for an object with custom ns
329 * @kobj: object we're creating for
330 * @attr: attribute descriptor
331 * @ns: namespace the new file should belong to
332 */
333int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
334 const void *ns)
335{
336 kuid_t uid;
337 kgid_t gid;
338
339 if (WARN_ON(!kobj || !kobj->sd || !attr))
340 return -EINVAL;
341
342 kobject_get_ownership(kobj, &uid, &gid);
343 return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode,
344 uid, gid, ns);
345
346}
347EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
348
349int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
350{
351 int err = 0;
352 int i;
353
354 for (i = 0; ptr[i] && !err; i++)
355 err = sysfs_create_file(kobj, ptr[i]);
356 if (err)
357 while (--i >= 0)
358 sysfs_remove_file(kobj, ptr[i]);
359 return err;
360}
361EXPORT_SYMBOL_GPL(sysfs_create_files);
362
363/**
364 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
365 * @kobj: object we're acting for.
366 * @attr: attribute descriptor.
367 * @group: group name.
368 */
369int sysfs_add_file_to_group(struct kobject *kobj,
370 const struct attribute *attr, const char *group)
371{
372 struct kernfs_node *parent;
373 kuid_t uid;
374 kgid_t gid;
375 int error;
376
377 if (group) {
378 parent = kernfs_find_and_get(kobj->sd, group);
379 } else {
380 parent = kobj->sd;
381 kernfs_get(parent);
382 }
383
384 if (!parent)
385 return -ENOENT;
386
387 kobject_get_ownership(kobj, &uid, &gid);
388 error = sysfs_add_file_mode_ns(parent, attr, false,
389 attr->mode, uid, gid, NULL);
390 kernfs_put(parent);
391
392 return error;
393}
394EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
395
396/**
397 * sysfs_chmod_file - update the modified mode value on an object attribute.
398 * @kobj: object we're acting for.
399 * @attr: attribute descriptor.
400 * @mode: file permissions.
401 *
402 */
403int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
404 umode_t mode)
405{
406 struct kernfs_node *kn;
407 struct iattr newattrs;
408 int rc;
409
410 kn = kernfs_find_and_get(kobj->sd, attr->name);
411 if (!kn)
412 return -ENOENT;
413
414 newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
415 newattrs.ia_valid = ATTR_MODE;
416
417 rc = kernfs_setattr(kn, &newattrs);
418
419 kernfs_put(kn);
420 return rc;
421}
422EXPORT_SYMBOL_GPL(sysfs_chmod_file);
423
424/**
425 * sysfs_break_active_protection - break "active" protection
426 * @kobj: The kernel object @attr is associated with.
427 * @attr: The attribute to break the "active" protection for.
428 *
429 * With sysfs, just like kernfs, deletion of an attribute is postponed until
430 * all active .show() and .store() callbacks have finished unless this function
431 * is called. Hence this function is useful in methods that implement self
432 * deletion.
433 */
434struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
435 const struct attribute *attr)
436{
437 struct kernfs_node *kn;
438
439 kobject_get(kobj);
440 kn = kernfs_find_and_get(kobj->sd, attr->name);
441 if (kn)
442 kernfs_break_active_protection(kn);
443 return kn;
444}
445EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
446
447/**
448 * sysfs_unbreak_active_protection - restore "active" protection
449 * @kn: Pointer returned by sysfs_break_active_protection().
450 *
451 * Undo the effects of sysfs_break_active_protection(). Since this function
452 * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
453 * argument passed to sysfs_break_active_protection() that attribute may have
454 * been removed between the sysfs_break_active_protection() and
455 * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
456 * this function has returned.
457 */
458void sysfs_unbreak_active_protection(struct kernfs_node *kn)
459{
460 struct kobject *kobj = kn->parent->priv;
461
462 kernfs_unbreak_active_protection(kn);
463 kernfs_put(kn);
464 kobject_put(kobj);
465}
466EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
467
468/**
469 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
470 * @kobj: object we're acting for
471 * @attr: attribute descriptor
472 * @ns: namespace tag of the file to remove
473 *
474 * Hash the attribute name and namespace tag and kill the victim.
475 */
476void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
477 const void *ns)
478{
479 struct kernfs_node *parent = kobj->sd;
480
481 kernfs_remove_by_name_ns(parent, attr->name, ns);
482}
483EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
484
485/**
486 * sysfs_remove_file_self - remove an object attribute from its own method
487 * @kobj: object we're acting for
488 * @attr: attribute descriptor
489 *
490 * See kernfs_remove_self() for details.
491 */
492bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
493{
494 struct kernfs_node *parent = kobj->sd;
495 struct kernfs_node *kn;
496 bool ret;
497
498 kn = kernfs_find_and_get(parent, attr->name);
499 if (WARN_ON_ONCE(!kn))
500 return false;
501
502 ret = kernfs_remove_self(kn);
503
504 kernfs_put(kn);
505 return ret;
506}
507EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
508
509void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
510{
511 int i;
512
513 for (i = 0; ptr[i]; i++)
514 sysfs_remove_file(kobj, ptr[i]);
515}
516EXPORT_SYMBOL_GPL(sysfs_remove_files);
517
518/**
519 * sysfs_remove_file_from_group - remove an attribute file from a group.
520 * @kobj: object we're acting for.
521 * @attr: attribute descriptor.
522 * @group: group name.
523 */
524void sysfs_remove_file_from_group(struct kobject *kobj,
525 const struct attribute *attr, const char *group)
526{
527 struct kernfs_node *parent;
528
529 if (group) {
530 parent = kernfs_find_and_get(kobj->sd, group);
531 } else {
532 parent = kobj->sd;
533 kernfs_get(parent);
534 }
535
536 if (parent) {
537 kernfs_remove_by_name(parent, attr->name);
538 kernfs_put(parent);
539 }
540}
541EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
542
543/**
544 * sysfs_create_bin_file - create binary file for object.
545 * @kobj: object.
546 * @attr: attribute descriptor.
547 */
548int sysfs_create_bin_file(struct kobject *kobj,
549 const struct bin_attribute *attr)
550{
551 kuid_t uid;
552 kgid_t gid;
553
554 if (WARN_ON(!kobj || !kobj->sd || !attr))
555 return -EINVAL;
556
557 kobject_get_ownership(kobj, &uid, &gid);
558 return sysfs_add_file_mode_ns(kobj->sd, &attr->attr, true,
559 attr->attr.mode, uid, gid, NULL);
560}
561EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
562
563/**
564 * sysfs_remove_bin_file - remove binary file for object.
565 * @kobj: object.
566 * @attr: attribute descriptor.
567 */
568void sysfs_remove_bin_file(struct kobject *kobj,
569 const struct bin_attribute *attr)
570{
571 kernfs_remove_by_name(kobj->sd, attr->attr.name);
572}
573EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
574
575static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
576 kgid_t kgid)
577{
578 struct iattr newattrs = {
579 .ia_valid = ATTR_UID | ATTR_GID,
580 .ia_uid = kuid,
581 .ia_gid = kgid,
582 };
583 return kernfs_setattr(kn, &newattrs);
584}
585
586/**
587 * sysfs_link_change_owner - change owner of a sysfs file.
588 * @kobj: object of the kernfs_node the symlink is located in.
589 * @targ: object of the kernfs_node the symlink points to.
590 * @name: name of the link.
591 * @kuid: new owner's kuid
592 * @kgid: new owner's kgid
593 *
594 * This function looks up the sysfs symlink entry @name under @kobj and changes
595 * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
596 * @targ.
597 *
598 * Returns 0 on success or error code on failure.
599 */
600int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
601 const char *name, kuid_t kuid, kgid_t kgid)
602{
603 struct kernfs_node *kn = NULL;
604 int error;
605
606 if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
607 return -EINVAL;
608
609 error = -ENOENT;
610 kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
611 if (!kn)
612 goto out;
613
614 error = -EINVAL;
615 if (kernfs_type(kn) != KERNFS_LINK)
616 goto out;
617 if (kn->symlink.target_kn->priv != targ)
618 goto out;
619
620 error = internal_change_owner(kn, kuid, kgid);
621
622out:
623 kernfs_put(kn);
624 return error;
625}
626
627/**
628 * sysfs_file_change_owner - change owner of a sysfs file.
629 * @kobj: object.
630 * @name: name of the file to change.
631 * @kuid: new owner's kuid
632 * @kgid: new owner's kgid
633 *
634 * This function looks up the sysfs entry @name under @kobj and changes the
635 * ownership to @kuid/@kgid.
636 *
637 * Returns 0 on success or error code on failure.
638 */
639int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
640 kgid_t kgid)
641{
642 struct kernfs_node *kn;
643 int error;
644
645 if (!name)
646 return -EINVAL;
647
648 if (!kobj->state_in_sysfs)
649 return -EINVAL;
650
651 kn = kernfs_find_and_get(kobj->sd, name);
652 if (!kn)
653 return -ENOENT;
654
655 error = internal_change_owner(kn, kuid, kgid);
656
657 kernfs_put(kn);
658
659 return error;
660}
661EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
662
663/**
664 * sysfs_change_owner - change owner of the given object.
665 * @kobj: object.
666 * @kuid: new owner's kuid
667 * @kgid: new owner's kgid
668 *
669 * Change the owner of the default directory, files, groups, and attributes of
670 * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
671 * entries for a kobject are added by driver core. In summary,
672 * sysfs_change_owner() takes care of the default directory entry for @kobj,
673 * the default attributes associated with the ktype of @kobj and the default
674 * attributes associated with the ktype of @kobj.
675 * Additional properties not added by driver core have to be changed by the
676 * driver or subsystem which created them. This is similar to how
677 * driver/subsystem specific entries are removed.
678 *
679 * Returns 0 on success or error code on failure.
680 */
681int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
682{
683 int error;
684 const struct kobj_type *ktype;
685
686 if (!kobj->state_in_sysfs)
687 return -EINVAL;
688
689 /* Change the owner of the kobject itself. */
690 error = internal_change_owner(kobj->sd, kuid, kgid);
691 if (error)
692 return error;
693
694 ktype = get_ktype(kobj);
695 if (ktype) {
696 struct attribute **kattr;
697
698 /*
699 * Change owner of the default attributes associated with the
700 * ktype of @kobj.
701 */
702 for (kattr = ktype->default_attrs; kattr && *kattr; kattr++) {
703 error = sysfs_file_change_owner(kobj, (*kattr)->name,
704 kuid, kgid);
705 if (error)
706 return error;
707 }
708
709 /*
710 * Change owner of the default groups associated with the
711 * ktype of @kobj.
712 */
713 error = sysfs_groups_change_owner(kobj, ktype->default_groups,
714 kuid, kgid);
715 if (error)
716 return error;
717 }
718
719 return 0;
720}
721EXPORT_SYMBOL_GPL(sysfs_change_owner);
722
723/**
724 * sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
725 * @buf: start of PAGE_SIZE buffer.
726 * @fmt: format
727 * @...: optional arguments to @format
728 *
729 *
730 * Returns number of characters written to @buf.
731 */
732int sysfs_emit(char *buf, const char *fmt, ...)
733{
734 va_list args;
735 int len;
736
737 if (WARN(!buf || offset_in_page(buf),
738 "invalid sysfs_emit: buf:%p\n", buf))
739 return 0;
740
741 va_start(args, fmt);
742 len = vscnprintf(buf, PAGE_SIZE, fmt, args);
743 va_end(args);
744
745 return len;
746}
747EXPORT_SYMBOL_GPL(sysfs_emit);
748
749/**
750 * sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
751 * @buf: start of PAGE_SIZE buffer.
752 * @at: offset in @buf to start write in bytes
753 * @at must be >= 0 && < PAGE_SIZE
754 * @fmt: format
755 * @...: optional arguments to @fmt
756 *
757 *
758 * Returns number of characters written starting at &@buf[@at].
759 */
760int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
761{
762 va_list args;
763 int len;
764
765 if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
766 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
767 return 0;
768
769 va_start(args, fmt);
770 len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
771 va_end(args);
772
773 return len;
774}
775EXPORT_SYMBOL_GPL(sysfs_emit_at);