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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 int sysfs_kf_bin_open(struct kernfs_open_file *of)
171{
172 struct bin_attribute *battr = of->kn->priv;
173
174 if (battr->f_mapping)
175 of->file->f_mapping = battr->f_mapping();
176
177 return 0;
178}
179
180void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
181{
182 struct kernfs_node *kn = kobj->sd, *tmp;
183
184 if (kn && dir)
185 kn = kernfs_find_and_get(kn, dir);
186 else
187 kernfs_get(kn);
188
189 if (kn && attr) {
190 tmp = kernfs_find_and_get(kn, attr);
191 kernfs_put(kn);
192 kn = tmp;
193 }
194
195 if (kn) {
196 kernfs_notify(kn);
197 kernfs_put(kn);
198 }
199}
200EXPORT_SYMBOL_GPL(sysfs_notify);
201
202static const struct kernfs_ops sysfs_file_kfops_empty = {
203};
204
205static const struct kernfs_ops sysfs_file_kfops_ro = {
206 .seq_show = sysfs_kf_seq_show,
207};
208
209static const struct kernfs_ops sysfs_file_kfops_wo = {
210 .write = sysfs_kf_write,
211};
212
213static const struct kernfs_ops sysfs_file_kfops_rw = {
214 .seq_show = sysfs_kf_seq_show,
215 .write = sysfs_kf_write,
216};
217
218static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
219 .read = sysfs_kf_read,
220 .prealloc = true,
221};
222
223static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
224 .write = sysfs_kf_write,
225 .prealloc = true,
226};
227
228static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
229 .read = sysfs_kf_read,
230 .write = sysfs_kf_write,
231 .prealloc = true,
232};
233
234static const struct kernfs_ops sysfs_bin_kfops_ro = {
235 .read = sysfs_kf_bin_read,
236};
237
238static const struct kernfs_ops sysfs_bin_kfops_wo = {
239 .write = sysfs_kf_bin_write,
240};
241
242static const struct kernfs_ops sysfs_bin_kfops_rw = {
243 .read = sysfs_kf_bin_read,
244 .write = sysfs_kf_bin_write,
245};
246
247static const struct kernfs_ops sysfs_bin_kfops_mmap = {
248 .read = sysfs_kf_bin_read,
249 .write = sysfs_kf_bin_write,
250 .mmap = sysfs_kf_bin_mmap,
251 .open = sysfs_kf_bin_open,
252};
253
254int sysfs_add_file_mode_ns(struct kernfs_node *parent,
255 const struct attribute *attr, umode_t mode, kuid_t uid,
256 kgid_t gid, const void *ns)
257{
258 struct kobject *kobj = parent->priv;
259 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
260 struct lock_class_key *key = NULL;
261 const struct kernfs_ops *ops = NULL;
262 struct kernfs_node *kn;
263
264 /* every kobject with an attribute needs a ktype assigned */
265 if (WARN(!sysfs_ops, KERN_ERR
266 "missing sysfs attribute operations for kobject: %s\n",
267 kobject_name(kobj)))
268 return -EINVAL;
269
270 if (mode & SYSFS_PREALLOC) {
271 if (sysfs_ops->show && sysfs_ops->store)
272 ops = &sysfs_prealloc_kfops_rw;
273 else if (sysfs_ops->show)
274 ops = &sysfs_prealloc_kfops_ro;
275 else if (sysfs_ops->store)
276 ops = &sysfs_prealloc_kfops_wo;
277 } else {
278 if (sysfs_ops->show && sysfs_ops->store)
279 ops = &sysfs_file_kfops_rw;
280 else if (sysfs_ops->show)
281 ops = &sysfs_file_kfops_ro;
282 else if (sysfs_ops->store)
283 ops = &sysfs_file_kfops_wo;
284 }
285
286 if (!ops)
287 ops = &sysfs_file_kfops_empty;
288
289#ifdef CONFIG_DEBUG_LOCK_ALLOC
290 if (!attr->ignore_lockdep)
291 key = attr->key ?: (struct lock_class_key *)&attr->skey;
292#endif
293
294 kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
295 PAGE_SIZE, ops, (void *)attr, ns, key);
296 if (IS_ERR(kn)) {
297 if (PTR_ERR(kn) == -EEXIST)
298 sysfs_warn_dup(parent, attr->name);
299 return PTR_ERR(kn);
300 }
301 return 0;
302}
303
304int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
305 const struct bin_attribute *battr, umode_t mode,
306 kuid_t uid, kgid_t gid, const void *ns)
307{
308 const struct attribute *attr = &battr->attr;
309 struct lock_class_key *key = NULL;
310 const struct kernfs_ops *ops;
311 struct kernfs_node *kn;
312
313 if (battr->mmap)
314 ops = &sysfs_bin_kfops_mmap;
315 else if (battr->read && battr->write)
316 ops = &sysfs_bin_kfops_rw;
317 else if (battr->read)
318 ops = &sysfs_bin_kfops_ro;
319 else if (battr->write)
320 ops = &sysfs_bin_kfops_wo;
321 else
322 ops = &sysfs_file_kfops_empty;
323
324#ifdef CONFIG_DEBUG_LOCK_ALLOC
325 if (!attr->ignore_lockdep)
326 key = attr->key ?: (struct lock_class_key *)&attr->skey;
327#endif
328
329 kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
330 battr->size, ops, (void *)attr, ns, key);
331 if (IS_ERR(kn)) {
332 if (PTR_ERR(kn) == -EEXIST)
333 sysfs_warn_dup(parent, attr->name);
334 return PTR_ERR(kn);
335 }
336 return 0;
337}
338
339/**
340 * sysfs_create_file_ns - create an attribute file for an object with custom ns
341 * @kobj: object we're creating for
342 * @attr: attribute descriptor
343 * @ns: namespace the new file should belong to
344 */
345int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
346 const void *ns)
347{
348 kuid_t uid;
349 kgid_t gid;
350
351 if (WARN_ON(!kobj || !kobj->sd || !attr))
352 return -EINVAL;
353
354 kobject_get_ownership(kobj, &uid, &gid);
355 return sysfs_add_file_mode_ns(kobj->sd, attr, attr->mode, uid, gid, ns);
356}
357EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
358
359int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
360{
361 int err = 0;
362 int i;
363
364 for (i = 0; ptr[i] && !err; i++)
365 err = sysfs_create_file(kobj, ptr[i]);
366 if (err)
367 while (--i >= 0)
368 sysfs_remove_file(kobj, ptr[i]);
369 return err;
370}
371EXPORT_SYMBOL_GPL(sysfs_create_files);
372
373/**
374 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
375 * @kobj: object we're acting for.
376 * @attr: attribute descriptor.
377 * @group: group name.
378 */
379int sysfs_add_file_to_group(struct kobject *kobj,
380 const struct attribute *attr, const char *group)
381{
382 struct kernfs_node *parent;
383 kuid_t uid;
384 kgid_t gid;
385 int error;
386
387 if (group) {
388 parent = kernfs_find_and_get(kobj->sd, group);
389 } else {
390 parent = kobj->sd;
391 kernfs_get(parent);
392 }
393
394 if (!parent)
395 return -ENOENT;
396
397 kobject_get_ownership(kobj, &uid, &gid);
398 error = sysfs_add_file_mode_ns(parent, attr, attr->mode, uid, gid,
399 NULL);
400 kernfs_put(parent);
401
402 return error;
403}
404EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
405
406/**
407 * sysfs_chmod_file - update the modified mode value on an object attribute.
408 * @kobj: object we're acting for.
409 * @attr: attribute descriptor.
410 * @mode: file permissions.
411 *
412 */
413int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
414 umode_t mode)
415{
416 struct kernfs_node *kn;
417 struct iattr newattrs;
418 int rc;
419
420 kn = kernfs_find_and_get(kobj->sd, attr->name);
421 if (!kn)
422 return -ENOENT;
423
424 newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
425 newattrs.ia_valid = ATTR_MODE;
426
427 rc = kernfs_setattr(kn, &newattrs);
428
429 kernfs_put(kn);
430 return rc;
431}
432EXPORT_SYMBOL_GPL(sysfs_chmod_file);
433
434/**
435 * sysfs_break_active_protection - break "active" protection
436 * @kobj: The kernel object @attr is associated with.
437 * @attr: The attribute to break the "active" protection for.
438 *
439 * With sysfs, just like kernfs, deletion of an attribute is postponed until
440 * all active .show() and .store() callbacks have finished unless this function
441 * is called. Hence this function is useful in methods that implement self
442 * deletion.
443 */
444struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
445 const struct attribute *attr)
446{
447 struct kernfs_node *kn;
448
449 kobject_get(kobj);
450 kn = kernfs_find_and_get(kobj->sd, attr->name);
451 if (kn)
452 kernfs_break_active_protection(kn);
453 return kn;
454}
455EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
456
457/**
458 * sysfs_unbreak_active_protection - restore "active" protection
459 * @kn: Pointer returned by sysfs_break_active_protection().
460 *
461 * Undo the effects of sysfs_break_active_protection(). Since this function
462 * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
463 * argument passed to sysfs_break_active_protection() that attribute may have
464 * been removed between the sysfs_break_active_protection() and
465 * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
466 * this function has returned.
467 */
468void sysfs_unbreak_active_protection(struct kernfs_node *kn)
469{
470 struct kobject *kobj = kn->parent->priv;
471
472 kernfs_unbreak_active_protection(kn);
473 kernfs_put(kn);
474 kobject_put(kobj);
475}
476EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
477
478/**
479 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
480 * @kobj: object we're acting for
481 * @attr: attribute descriptor
482 * @ns: namespace tag of the file to remove
483 *
484 * Hash the attribute name and namespace tag and kill the victim.
485 */
486void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
487 const void *ns)
488{
489 struct kernfs_node *parent = kobj->sd;
490
491 kernfs_remove_by_name_ns(parent, attr->name, ns);
492}
493EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
494
495/**
496 * sysfs_remove_file_self - remove an object attribute from its own method
497 * @kobj: object we're acting for
498 * @attr: attribute descriptor
499 *
500 * See kernfs_remove_self() for details.
501 */
502bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
503{
504 struct kernfs_node *parent = kobj->sd;
505 struct kernfs_node *kn;
506 bool ret;
507
508 kn = kernfs_find_and_get(parent, attr->name);
509 if (WARN_ON_ONCE(!kn))
510 return false;
511
512 ret = kernfs_remove_self(kn);
513
514 kernfs_put(kn);
515 return ret;
516}
517EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
518
519void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
520{
521 int i;
522
523 for (i = 0; ptr[i]; i++)
524 sysfs_remove_file(kobj, ptr[i]);
525}
526EXPORT_SYMBOL_GPL(sysfs_remove_files);
527
528/**
529 * sysfs_remove_file_from_group - remove an attribute file from a group.
530 * @kobj: object we're acting for.
531 * @attr: attribute descriptor.
532 * @group: group name.
533 */
534void sysfs_remove_file_from_group(struct kobject *kobj,
535 const struct attribute *attr, const char *group)
536{
537 struct kernfs_node *parent;
538
539 if (group) {
540 parent = kernfs_find_and_get(kobj->sd, group);
541 } else {
542 parent = kobj->sd;
543 kernfs_get(parent);
544 }
545
546 if (parent) {
547 kernfs_remove_by_name(parent, attr->name);
548 kernfs_put(parent);
549 }
550}
551EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
552
553/**
554 * sysfs_create_bin_file - create binary file for object.
555 * @kobj: object.
556 * @attr: attribute descriptor.
557 */
558int sysfs_create_bin_file(struct kobject *kobj,
559 const struct bin_attribute *attr)
560{
561 kuid_t uid;
562 kgid_t gid;
563
564 if (WARN_ON(!kobj || !kobj->sd || !attr))
565 return -EINVAL;
566
567 kobject_get_ownership(kobj, &uid, &gid);
568 return sysfs_add_bin_file_mode_ns(kobj->sd, attr, attr->attr.mode, uid,
569 gid, NULL);
570}
571EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
572
573/**
574 * sysfs_remove_bin_file - remove binary file for object.
575 * @kobj: object.
576 * @attr: attribute descriptor.
577 */
578void sysfs_remove_bin_file(struct kobject *kobj,
579 const struct bin_attribute *attr)
580{
581 kernfs_remove_by_name(kobj->sd, attr->attr.name);
582}
583EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
584
585static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
586 kgid_t kgid)
587{
588 struct iattr newattrs = {
589 .ia_valid = ATTR_UID | ATTR_GID,
590 .ia_uid = kuid,
591 .ia_gid = kgid,
592 };
593 return kernfs_setattr(kn, &newattrs);
594}
595
596/**
597 * sysfs_link_change_owner - change owner of a sysfs file.
598 * @kobj: object of the kernfs_node the symlink is located in.
599 * @targ: object of the kernfs_node the symlink points to.
600 * @name: name of the link.
601 * @kuid: new owner's kuid
602 * @kgid: new owner's kgid
603 *
604 * This function looks up the sysfs symlink entry @name under @kobj and changes
605 * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
606 * @targ.
607 *
608 * Returns 0 on success or error code on failure.
609 */
610int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
611 const char *name, kuid_t kuid, kgid_t kgid)
612{
613 struct kernfs_node *kn = NULL;
614 int error;
615
616 if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
617 return -EINVAL;
618
619 error = -ENOENT;
620 kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
621 if (!kn)
622 goto out;
623
624 error = -EINVAL;
625 if (kernfs_type(kn) != KERNFS_LINK)
626 goto out;
627 if (kn->symlink.target_kn->priv != targ)
628 goto out;
629
630 error = internal_change_owner(kn, kuid, kgid);
631
632out:
633 kernfs_put(kn);
634 return error;
635}
636
637/**
638 * sysfs_file_change_owner - change owner of a sysfs file.
639 * @kobj: object.
640 * @name: name of the file to change.
641 * @kuid: new owner's kuid
642 * @kgid: new owner's kgid
643 *
644 * This function looks up the sysfs entry @name under @kobj and changes the
645 * ownership to @kuid/@kgid.
646 *
647 * Returns 0 on success or error code on failure.
648 */
649int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
650 kgid_t kgid)
651{
652 struct kernfs_node *kn;
653 int error;
654
655 if (!name)
656 return -EINVAL;
657
658 if (!kobj->state_in_sysfs)
659 return -EINVAL;
660
661 kn = kernfs_find_and_get(kobj->sd, name);
662 if (!kn)
663 return -ENOENT;
664
665 error = internal_change_owner(kn, kuid, kgid);
666
667 kernfs_put(kn);
668
669 return error;
670}
671EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
672
673/**
674 * sysfs_change_owner - change owner of the given object.
675 * @kobj: object.
676 * @kuid: new owner's kuid
677 * @kgid: new owner's kgid
678 *
679 * Change the owner of the default directory, files, groups, and attributes of
680 * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
681 * entries for a kobject are added by driver core. In summary,
682 * sysfs_change_owner() takes care of the default directory entry for @kobj,
683 * the default attributes associated with the ktype of @kobj and the default
684 * attributes associated with the ktype of @kobj.
685 * Additional properties not added by driver core have to be changed by the
686 * driver or subsystem which created them. This is similar to how
687 * driver/subsystem specific entries are removed.
688 *
689 * Returns 0 on success or error code on failure.
690 */
691int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
692{
693 int error;
694 const struct kobj_type *ktype;
695
696 if (!kobj->state_in_sysfs)
697 return -EINVAL;
698
699 /* Change the owner of the kobject itself. */
700 error = internal_change_owner(kobj->sd, kuid, kgid);
701 if (error)
702 return error;
703
704 ktype = get_ktype(kobj);
705 if (ktype) {
706 /*
707 * Change owner of the default groups associated with the
708 * ktype of @kobj.
709 */
710 error = sysfs_groups_change_owner(kobj, ktype->default_groups,
711 kuid, kgid);
712 if (error)
713 return error;
714 }
715
716 return 0;
717}
718EXPORT_SYMBOL_GPL(sysfs_change_owner);
719
720/**
721 * sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
722 * @buf: start of PAGE_SIZE buffer.
723 * @fmt: format
724 * @...: optional arguments to @format
725 *
726 *
727 * Returns number of characters written to @buf.
728 */
729int sysfs_emit(char *buf, const char *fmt, ...)
730{
731 va_list args;
732 int len;
733
734 if (WARN(!buf || offset_in_page(buf),
735 "invalid sysfs_emit: buf:%p\n", buf))
736 return 0;
737
738 va_start(args, fmt);
739 len = vscnprintf(buf, PAGE_SIZE, fmt, args);
740 va_end(args);
741
742 return len;
743}
744EXPORT_SYMBOL_GPL(sysfs_emit);
745
746/**
747 * sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
748 * @buf: start of PAGE_SIZE buffer.
749 * @at: offset in @buf to start write in bytes
750 * @at must be >= 0 && < PAGE_SIZE
751 * @fmt: format
752 * @...: optional arguments to @fmt
753 *
754 *
755 * Returns number of characters written starting at &@buf[@at].
756 */
757int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
758{
759 va_list args;
760 int len;
761
762 if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
763 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
764 return 0;
765
766 va_start(args, fmt);
767 len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
768 va_end(args);
769
770 return len;
771}
772EXPORT_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 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 else
467 kobject_put(kobj);
468 return kn;
469}
470EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
471
472/**
473 * sysfs_unbreak_active_protection - restore "active" protection
474 * @kn: Pointer returned by sysfs_break_active_protection().
475 *
476 * Undo the effects of sysfs_break_active_protection(). Since this function
477 * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
478 * argument passed to sysfs_break_active_protection() that attribute may have
479 * been removed between the sysfs_break_active_protection() and
480 * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
481 * this function has returned.
482 */
483void sysfs_unbreak_active_protection(struct kernfs_node *kn)
484{
485 struct kobject *kobj = kn->parent->priv;
486
487 kernfs_unbreak_active_protection(kn);
488 kernfs_put(kn);
489 kobject_put(kobj);
490}
491EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
492
493/**
494 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
495 * @kobj: object we're acting for
496 * @attr: attribute descriptor
497 * @ns: namespace tag of the file to remove
498 *
499 * Hash the attribute name and namespace tag and kill the victim.
500 */
501void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
502 const void *ns)
503{
504 struct kernfs_node *parent = kobj->sd;
505
506 kernfs_remove_by_name_ns(parent, attr->name, ns);
507}
508EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
509
510/**
511 * sysfs_remove_file_self - remove an object attribute from its own method
512 * @kobj: object we're acting for
513 * @attr: attribute descriptor
514 *
515 * See kernfs_remove_self() for details.
516 */
517bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
518{
519 struct kernfs_node *parent = kobj->sd;
520 struct kernfs_node *kn;
521 bool ret;
522
523 kn = kernfs_find_and_get(parent, attr->name);
524 if (WARN_ON_ONCE(!kn))
525 return false;
526
527 ret = kernfs_remove_self(kn);
528
529 kernfs_put(kn);
530 return ret;
531}
532EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
533
534void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
535{
536 int i;
537
538 for (i = 0; ptr[i]; i++)
539 sysfs_remove_file(kobj, ptr[i]);
540}
541EXPORT_SYMBOL_GPL(sysfs_remove_files);
542
543/**
544 * sysfs_remove_file_from_group - remove an attribute file from a group.
545 * @kobj: object we're acting for.
546 * @attr: attribute descriptor.
547 * @group: group name.
548 */
549void sysfs_remove_file_from_group(struct kobject *kobj,
550 const struct attribute *attr, const char *group)
551{
552 struct kernfs_node *parent;
553
554 if (group) {
555 parent = kernfs_find_and_get(kobj->sd, group);
556 } else {
557 parent = kobj->sd;
558 kernfs_get(parent);
559 }
560
561 if (parent) {
562 kernfs_remove_by_name(parent, attr->name);
563 kernfs_put(parent);
564 }
565}
566EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
567
568/**
569 * sysfs_create_bin_file - create binary file for object.
570 * @kobj: object.
571 * @attr: attribute descriptor.
572 */
573int sysfs_create_bin_file(struct kobject *kobj,
574 const struct bin_attribute *attr)
575{
576 kuid_t uid;
577 kgid_t gid;
578
579 if (WARN_ON(!kobj || !kobj->sd || !attr))
580 return -EINVAL;
581
582 kobject_get_ownership(kobj, &uid, &gid);
583 return sysfs_add_bin_file_mode_ns(kobj->sd, attr, attr->attr.mode, uid,
584 gid, NULL);
585}
586EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
587
588/**
589 * sysfs_remove_bin_file - remove binary file for object.
590 * @kobj: object.
591 * @attr: attribute descriptor.
592 */
593void sysfs_remove_bin_file(struct kobject *kobj,
594 const struct bin_attribute *attr)
595{
596 kernfs_remove_by_name(kobj->sd, attr->attr.name);
597}
598EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
599
600static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
601 kgid_t kgid)
602{
603 struct iattr newattrs = {
604 .ia_valid = ATTR_UID | ATTR_GID,
605 .ia_uid = kuid,
606 .ia_gid = kgid,
607 };
608 return kernfs_setattr(kn, &newattrs);
609}
610
611/**
612 * sysfs_link_change_owner - change owner of a sysfs file.
613 * @kobj: object of the kernfs_node the symlink is located in.
614 * @targ: object of the kernfs_node the symlink points to.
615 * @name: name of the link.
616 * @kuid: new owner's kuid
617 * @kgid: new owner's kgid
618 *
619 * This function looks up the sysfs symlink entry @name under @kobj and changes
620 * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
621 * @targ.
622 *
623 * Returns 0 on success or error code on failure.
624 */
625int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
626 const char *name, kuid_t kuid, kgid_t kgid)
627{
628 struct kernfs_node *kn = NULL;
629 int error;
630
631 if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
632 return -EINVAL;
633
634 error = -ENOENT;
635 kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
636 if (!kn)
637 goto out;
638
639 error = -EINVAL;
640 if (kernfs_type(kn) != KERNFS_LINK)
641 goto out;
642 if (kn->symlink.target_kn->priv != targ)
643 goto out;
644
645 error = internal_change_owner(kn, kuid, kgid);
646
647out:
648 kernfs_put(kn);
649 return error;
650}
651
652/**
653 * sysfs_file_change_owner - change owner of a sysfs file.
654 * @kobj: object.
655 * @name: name of the file to change.
656 * @kuid: new owner's kuid
657 * @kgid: new owner's kgid
658 *
659 * This function looks up the sysfs entry @name under @kobj and changes the
660 * ownership to @kuid/@kgid.
661 *
662 * Returns 0 on success or error code on failure.
663 */
664int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
665 kgid_t kgid)
666{
667 struct kernfs_node *kn;
668 int error;
669
670 if (!name)
671 return -EINVAL;
672
673 if (!kobj->state_in_sysfs)
674 return -EINVAL;
675
676 kn = kernfs_find_and_get(kobj->sd, name);
677 if (!kn)
678 return -ENOENT;
679
680 error = internal_change_owner(kn, kuid, kgid);
681
682 kernfs_put(kn);
683
684 return error;
685}
686EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
687
688/**
689 * sysfs_change_owner - change owner of the given object.
690 * @kobj: object.
691 * @kuid: new owner's kuid
692 * @kgid: new owner's kgid
693 *
694 * Change the owner of the default directory, files, groups, and attributes of
695 * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
696 * entries for a kobject are added by driver core. In summary,
697 * sysfs_change_owner() takes care of the default directory entry for @kobj,
698 * the default attributes associated with the ktype of @kobj and the default
699 * attributes associated with the ktype of @kobj.
700 * Additional properties not added by driver core have to be changed by the
701 * driver or subsystem which created them. This is similar to how
702 * driver/subsystem specific entries are removed.
703 *
704 * Returns 0 on success or error code on failure.
705 */
706int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
707{
708 int error;
709 const struct kobj_type *ktype;
710
711 if (!kobj->state_in_sysfs)
712 return -EINVAL;
713
714 /* Change the owner of the kobject itself. */
715 error = internal_change_owner(kobj->sd, kuid, kgid);
716 if (error)
717 return error;
718
719 ktype = get_ktype(kobj);
720 if (ktype) {
721 /*
722 * Change owner of the default groups associated with the
723 * ktype of @kobj.
724 */
725 error = sysfs_groups_change_owner(kobj, ktype->default_groups,
726 kuid, kgid);
727 if (error)
728 return error;
729 }
730
731 return 0;
732}
733EXPORT_SYMBOL_GPL(sysfs_change_owner);
734
735/**
736 * sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
737 * @buf: start of PAGE_SIZE buffer.
738 * @fmt: format
739 * @...: optional arguments to @format
740 *
741 *
742 * Returns number of characters written to @buf.
743 */
744int sysfs_emit(char *buf, const char *fmt, ...)
745{
746 va_list args;
747 int len;
748
749 if (WARN(!buf || offset_in_page(buf),
750 "invalid sysfs_emit: buf:%p\n", buf))
751 return 0;
752
753 va_start(args, fmt);
754 len = vscnprintf(buf, PAGE_SIZE, fmt, args);
755 va_end(args);
756
757 return len;
758}
759EXPORT_SYMBOL_GPL(sysfs_emit);
760
761/**
762 * sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
763 * @buf: start of PAGE_SIZE buffer.
764 * @at: offset in @buf to start write in bytes
765 * @at must be >= 0 && < PAGE_SIZE
766 * @fmt: format
767 * @...: optional arguments to @fmt
768 *
769 *
770 * Returns number of characters written starting at &@buf[@at].
771 */
772int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
773{
774 va_list args;
775 int len;
776
777 if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
778 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
779 return 0;
780
781 va_start(args, fmt);
782 len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
783 va_end(args);
784
785 return len;
786}
787EXPORT_SYMBOL_GPL(sysfs_emit_at);