file.c

  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
 22static struct kobject *sysfs_file_kobj(struct kernfs_node *kn)
 23{
 24	guard(rcu)();
 25	return rcu_dereference(kn->__parent)->priv;
 26}
 27
 28/*
 29 * Determine ktype->sysfs_ops for the given kernfs_node.  This function
 30 * must be called while holding an active reference.
 31 */
 32static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
 33{
 34	struct kobject *kobj = sysfs_file_kobj(kn);
 35
 36	if (kn->flags & KERNFS_LOCKDEP)
 37		lockdep_assert_held(kn);
 38	return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
 39}
 40
 41/*
 42 * Reads on sysfs are handled through seq_file, which takes care of hairy
 43 * details like buffering and seeking.  The following function pipes
 44 * sysfs_ops->show() result through seq_file.
 45 */
 46static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
 47{
 48	struct kernfs_open_file *of = sf->private;
 49	struct kobject *kobj = sysfs_file_kobj(of->kn);
 50	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 51	ssize_t count;
 52	char *buf;
 53
 54	if (WARN_ON_ONCE(!ops->show))
 55		return -EINVAL;
 56
 57	/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
 58	count = seq_get_buf(sf, &buf);
 59	if (count < PAGE_SIZE) {
 60		seq_commit(sf, -1);
 61		return 0;
 62	}
 63	memset(buf, 0, PAGE_SIZE);
 64
 65	count = ops->show(kobj, of->kn->priv, buf);
 66	if (count < 0)
 67		return count;
 68
 69	/*
 70	 * The code works fine with PAGE_SIZE return but it's likely to
 71	 * indicate truncated result or overflow in normal use cases.
 72	 */
 73	if (count >= (ssize_t)PAGE_SIZE) {
 74		printk("fill_read_buffer: %pS returned bad count\n",
 75				ops->show);
 76		/* Try to struggle along */
 77		count = PAGE_SIZE - 1;
 78	}
 79	seq_commit(sf, count);
 80	return 0;
 81}
 82
 83static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
 84				 size_t count, loff_t pos)
 85{
 86	const struct bin_attribute *battr = of->kn->priv;
 87	struct kobject *kobj = sysfs_file_kobj(of->kn);
 88	loff_t size = file_inode(of->file)->i_size;
 89
 90	if (!count)
 91		return 0;
 92
 93	if (size) {
 94		if (pos >= size)
 95			return 0;
 96		if (pos + count > size)
 97			count = size - pos;
 98	}
 99
100	if (!battr->read)
101		return -EIO;
102
103	return battr->read(of->file, kobj, battr, buf, pos, count);
104}
105
106/* kernfs read callback for regular sysfs files with pre-alloc */
107static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
108			     size_t count, loff_t pos)
109{
110	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
111	struct kobject *kobj = sysfs_file_kobj(of->kn);
112	ssize_t len;
113
114	/*
115	 * If buf != of->prealloc_buf, we don't know how
116	 * large it is, so cannot safely pass it to ->show
117	 */
118	if (WARN_ON_ONCE(buf != of->prealloc_buf))
119		return 0;
120	len = ops->show(kobj, of->kn->priv, buf);
121	if (len < 0)
122		return len;
123	if (pos) {
124		if (len <= pos)
125			return 0;
126		len -= pos;
127		memmove(buf, buf + pos, len);
128	}
129	return min_t(ssize_t, count, len);
130}
131
132/* kernfs write callback for regular sysfs files */
133static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
134			      size_t count, loff_t pos)
135{
136	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
137	struct kobject *kobj = sysfs_file_kobj(of->kn);
138
139	if (!count)
140		return 0;
141
142	return ops->store(kobj, of->kn->priv, buf, count);
143}
144
145/* kernfs write callback for bin sysfs files */
146static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
147				  size_t count, loff_t pos)
148{
149	const struct bin_attribute *battr = of->kn->priv;
150	struct kobject *kobj = sysfs_file_kobj(of->kn);
151	loff_t size = file_inode(of->file)->i_size;
152
153	if (size) {
154		if (size <= pos)
155			return -EFBIG;
156		count = min_t(ssize_t, count, size - pos);
157	}
158	if (!count)
159		return 0;
160
161	if (!battr->write)
162		return -EIO;
163
164	return battr->write(of->file, kobj, battr, buf, pos, count);
165}
166
167static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
168			     struct vm_area_struct *vma)
169{
170	const struct bin_attribute *battr = of->kn->priv;
171	struct kobject *kobj = sysfs_file_kobj(of->kn);
172
173	return battr->mmap(of->file, kobj, battr, vma);
174}
175
176static loff_t sysfs_kf_bin_llseek(struct kernfs_open_file *of, loff_t offset,
177				  int whence)
178{
179	const struct bin_attribute *battr = of->kn->priv;
180	struct kobject *kobj = sysfs_file_kobj(of->kn);
181
182	if (battr->llseek)
183		return battr->llseek(of->file, kobj, battr, offset, whence);
184	else
185		return generic_file_llseek(of->file, offset, whence);
186}
187
188static int sysfs_kf_bin_open(struct kernfs_open_file *of)
189{
190	const struct bin_attribute *battr = of->kn->priv;
191
192	if (battr->f_mapping)
193		of->file->f_mapping = battr->f_mapping();
194
195	return 0;
196}
197
198void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
199{
200	struct kernfs_node *kn = kobj->sd, *tmp;
201
202	if (kn && dir)
203		kn = kernfs_find_and_get(kn, dir);
204	else
205		kernfs_get(kn);
206
207	if (kn && attr) {
208		tmp = kernfs_find_and_get(kn, attr);
209		kernfs_put(kn);
210		kn = tmp;
211	}
212
213	if (kn) {
214		kernfs_notify(kn);
215		kernfs_put(kn);
216	}
217}
218EXPORT_SYMBOL_GPL(sysfs_notify);
219
220static const struct kernfs_ops sysfs_file_kfops_empty = {
221};
222
223static const struct kernfs_ops sysfs_file_kfops_ro = {
224	.seq_show	= sysfs_kf_seq_show,
225};
226
227static const struct kernfs_ops sysfs_file_kfops_wo = {
228	.write		= sysfs_kf_write,
229};
230
231static const struct kernfs_ops sysfs_file_kfops_rw = {
232	.seq_show	= sysfs_kf_seq_show,
233	.write		= sysfs_kf_write,
234};
235
236static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
237	.read		= sysfs_kf_read,
238	.prealloc	= true,
239};
240
241static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
242	.write		= sysfs_kf_write,
243	.prealloc	= true,
244};
245
246static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
247	.read		= sysfs_kf_read,
248	.write		= sysfs_kf_write,
249	.prealloc	= true,
250};
251
252static const struct kernfs_ops sysfs_bin_kfops_ro = {
253	.read		= sysfs_kf_bin_read,
254};
255
256static const struct kernfs_ops sysfs_bin_kfops_wo = {
257	.write		= sysfs_kf_bin_write,
258};
259
260static const struct kernfs_ops sysfs_bin_kfops_rw = {
261	.read		= sysfs_kf_bin_read,
262	.write		= sysfs_kf_bin_write,
263};
264
265static const struct kernfs_ops sysfs_bin_kfops_mmap = {
266	.read		= sysfs_kf_bin_read,
267	.write		= sysfs_kf_bin_write,
268	.mmap		= sysfs_kf_bin_mmap,
269	.open		= sysfs_kf_bin_open,
270	.llseek		= sysfs_kf_bin_llseek,
271};
272
273int sysfs_add_file_mode_ns(struct kernfs_node *parent,
274		const struct attribute *attr, umode_t mode, kuid_t uid,
275		kgid_t gid, const void *ns)
276{
277	struct kobject *kobj = parent->priv;
278	const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
279	struct lock_class_key *key = NULL;
280	const struct kernfs_ops *ops = NULL;
281	struct kernfs_node *kn;
282
283	/* every kobject with an attribute needs a ktype assigned */
284	if (WARN(!sysfs_ops, KERN_ERR
285			"missing sysfs attribute operations for kobject: %s\n",
286			kobject_name(kobj)))
287		return -EINVAL;
288
289	if (mode & SYSFS_PREALLOC) {
290		if (sysfs_ops->show && sysfs_ops->store)
291			ops = &sysfs_prealloc_kfops_rw;
292		else if (sysfs_ops->show)
293			ops = &sysfs_prealloc_kfops_ro;
294		else if (sysfs_ops->store)
295			ops = &sysfs_prealloc_kfops_wo;
296	} else {
297		if (sysfs_ops->show && sysfs_ops->store)
298			ops = &sysfs_file_kfops_rw;
299		else if (sysfs_ops->show)
300			ops = &sysfs_file_kfops_ro;
301		else if (sysfs_ops->store)
302			ops = &sysfs_file_kfops_wo;
303	}
304
305	if (!ops)
306		ops = &sysfs_file_kfops_empty;
307
308#ifdef CONFIG_DEBUG_LOCK_ALLOC
309	if (!attr->ignore_lockdep)
310		key = attr->key ?: (struct lock_class_key *)&attr->skey;
311#endif
312
313	kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
314				  PAGE_SIZE, ops, (void *)attr, ns, key);
315	if (IS_ERR(kn)) {
316		if (PTR_ERR(kn) == -EEXIST)
317			sysfs_warn_dup(parent, attr->name);
318		return PTR_ERR(kn);
319	}
320	return 0;
321}
322
323int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
324		const struct bin_attribute *battr, umode_t mode, size_t size,
325		kuid_t uid, kgid_t gid, const void *ns)
326{
327	const struct attribute *attr = &battr->attr;
328	struct lock_class_key *key = NULL;
329	const struct kernfs_ops *ops;
330	struct kernfs_node *kn;
331
332	if (battr->mmap)
333		ops = &sysfs_bin_kfops_mmap;
334	else if (battr->read && battr->write)
335		ops = &sysfs_bin_kfops_rw;
336	else if (battr->read)
337		ops = &sysfs_bin_kfops_ro;
338	else if (battr->write)
339		ops = &sysfs_bin_kfops_wo;
340	else
341		ops = &sysfs_file_kfops_empty;
342
343#ifdef CONFIG_DEBUG_LOCK_ALLOC
344	if (!attr->ignore_lockdep)
345		key = attr->key ?: (struct lock_class_key *)&attr->skey;
346#endif
347
348	kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
349				  size, ops, (void *)attr, ns, key);
350	if (IS_ERR(kn)) {
351		if (PTR_ERR(kn) == -EEXIST)
352			sysfs_warn_dup(parent, attr->name);
353		return PTR_ERR(kn);
354	}
355	return 0;
356}
357
358/**
359 * sysfs_create_file_ns - create an attribute file for an object with custom ns
360 * @kobj: object we're creating for
361 * @attr: attribute descriptor
362 * @ns: namespace the new file should belong to
363 */
364int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
365			 const void *ns)
366{
367	kuid_t uid;
368	kgid_t gid;
369
370	if (WARN_ON(!kobj || !kobj->sd || !attr))
371		return -EINVAL;
372
373	kobject_get_ownership(kobj, &uid, &gid);
374	return sysfs_add_file_mode_ns(kobj->sd, attr, attr->mode, uid, gid, ns);
375}
376EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
377
378int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
379{
380	int err = 0;
381	int i;
382
383	for (i = 0; ptr[i] && !err; i++)
384		err = sysfs_create_file(kobj, ptr[i]);
385	if (err)
386		while (--i >= 0)
387			sysfs_remove_file(kobj, ptr[i]);
388	return err;
389}
390EXPORT_SYMBOL_GPL(sysfs_create_files);
391
392/**
393 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
394 * @kobj: object we're acting for.
395 * @attr: attribute descriptor.
396 * @group: group name.
397 */
398int sysfs_add_file_to_group(struct kobject *kobj,
399		const struct attribute *attr, const char *group)
400{
401	struct kernfs_node *parent;
402	kuid_t uid;
403	kgid_t gid;
404	int error;
405
406	if (group) {
407		parent = kernfs_find_and_get(kobj->sd, group);
408	} else {
409		parent = kobj->sd;
410		kernfs_get(parent);
411	}
412
413	if (!parent)
414		return -ENOENT;
415
416	kobject_get_ownership(kobj, &uid, &gid);
417	error = sysfs_add_file_mode_ns(parent, attr, attr->mode, uid, gid,
418				       NULL);
419	kernfs_put(parent);
420
421	return error;
422}
423EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
424
425/**
426 * sysfs_chmod_file - update the modified mode value on an object attribute.
427 * @kobj: object we're acting for.
428 * @attr: attribute descriptor.
429 * @mode: file permissions.
430 *
431 */
432int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
433		     umode_t mode)
434{
435	struct kernfs_node *kn;
436	struct iattr newattrs;
437	int rc;
438
439	kn = kernfs_find_and_get(kobj->sd, attr->name);
440	if (!kn)
441		return -ENOENT;
442
443	newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
444	newattrs.ia_valid = ATTR_MODE;
445
446	rc = kernfs_setattr(kn, &newattrs);
447
448	kernfs_put(kn);
449	return rc;
450}
451EXPORT_SYMBOL_GPL(sysfs_chmod_file);
452
453/**
454 * sysfs_break_active_protection - break "active" protection
455 * @kobj: The kernel object @attr is associated with.
456 * @attr: The attribute to break the "active" protection for.
457 *
458 * With sysfs, just like kernfs, deletion of an attribute is postponed until
459 * all active .show() and .store() callbacks have finished unless this function
460 * is called. Hence this function is useful in methods that implement self
461 * deletion.
462 */
463struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
464						  const struct attribute *attr)
465{
466	struct kernfs_node *kn;
467
468	kobject_get(kobj);
469	kn = kernfs_find_and_get(kobj->sd, attr->name);
470	if (kn)
471		kernfs_break_active_protection(kn);
472	else
473		kobject_put(kobj);
474	return kn;
475}
476EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
477
478/**
479 * sysfs_unbreak_active_protection - restore "active" protection
480 * @kn: Pointer returned by sysfs_break_active_protection().
481 *
482 * Undo the effects of sysfs_break_active_protection(). Since this function
483 * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
484 * argument passed to sysfs_break_active_protection() that attribute may have
485 * been removed between the sysfs_break_active_protection() and
486 * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
487 * this function has returned.
488 */
489void sysfs_unbreak_active_protection(struct kernfs_node *kn)
490{
491	struct kobject *kobj = sysfs_file_kobj(kn);
492
493	kernfs_unbreak_active_protection(kn);
494	kernfs_put(kn);
495	kobject_put(kobj);
496}
497EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
498
499/**
500 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
501 * @kobj: object we're acting for
502 * @attr: attribute descriptor
503 * @ns: namespace tag of the file to remove
504 *
505 * Hash the attribute name and namespace tag and kill the victim.
506 */
507void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
508			  const void *ns)
509{
510	struct kernfs_node *parent = kobj->sd;
511
512	kernfs_remove_by_name_ns(parent, attr->name, ns);
513}
514EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
515
516/**
517 * sysfs_remove_file_self - remove an object attribute from its own method
518 * @kobj: object we're acting for
519 * @attr: attribute descriptor
520 *
521 * See kernfs_remove_self() for details.
522 */
523bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
524{
525	struct kernfs_node *parent = kobj->sd;
526	struct kernfs_node *kn;
527	bool ret;
528
529	kn = kernfs_find_and_get(parent, attr->name);
530	if (WARN_ON_ONCE(!kn))
531		return false;
532
533	ret = kernfs_remove_self(kn);
534
535	kernfs_put(kn);
536	return ret;
537}
538EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
539
540void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
541{
542	int i;
543
544	for (i = 0; ptr[i]; i++)
545		sysfs_remove_file(kobj, ptr[i]);
546}
547EXPORT_SYMBOL_GPL(sysfs_remove_files);
548
549/**
550 * sysfs_remove_file_from_group - remove an attribute file from a group.
551 * @kobj: object we're acting for.
552 * @attr: attribute descriptor.
553 * @group: group name.
554 */
555void sysfs_remove_file_from_group(struct kobject *kobj,
556		const struct attribute *attr, const char *group)
557{
558	struct kernfs_node *parent;
559
560	if (group) {
561		parent = kernfs_find_and_get(kobj->sd, group);
562	} else {
563		parent = kobj->sd;
564		kernfs_get(parent);
565	}
566
567	if (parent) {
568		kernfs_remove_by_name(parent, attr->name);
569		kernfs_put(parent);
570	}
571}
572EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
573
574/**
575 *	sysfs_create_bin_file - create binary file for object.
576 *	@kobj:	object.
577 *	@attr:	attribute descriptor.
578 */
579int sysfs_create_bin_file(struct kobject *kobj,
580			  const struct bin_attribute *attr)
581{
582	kuid_t uid;
583	kgid_t gid;
584
585	if (WARN_ON(!kobj || !kobj->sd || !attr))
586		return -EINVAL;
587
588	kobject_get_ownership(kobj, &uid, &gid);
589	return sysfs_add_bin_file_mode_ns(kobj->sd, attr, attr->attr.mode,
590					  attr->size, uid, gid, NULL);
591}
592EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
593
594/**
595 *	sysfs_remove_bin_file - remove binary file for object.
596 *	@kobj:	object.
597 *	@attr:	attribute descriptor.
598 */
599void sysfs_remove_bin_file(struct kobject *kobj,
600			   const struct bin_attribute *attr)
601{
602	kernfs_remove_by_name(kobj->sd, attr->attr.name);
603}
604EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
605
606static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
607				 kgid_t kgid)
608{
609	struct iattr newattrs = {
610		.ia_valid = ATTR_UID | ATTR_GID,
611		.ia_uid = kuid,
612		.ia_gid = kgid,
613	};
614	return kernfs_setattr(kn, &newattrs);
615}
616
617/**
618 *	sysfs_link_change_owner - change owner of a sysfs file.
619 *	@kobj:	object of the kernfs_node the symlink is located in.
620 *	@targ:	object of the kernfs_node the symlink points to.
621 *	@name:	name of the link.
622 *	@kuid:	new owner's kuid
623 *	@kgid:	new owner's kgid
624 *
625 * This function looks up the sysfs symlink entry @name under @kobj and changes
626 * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
627 * @targ.
628 *
629 * Returns 0 on success or error code on failure.
630 */
631int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
632			    const char *name, kuid_t kuid, kgid_t kgid)
633{
634	struct kernfs_node *kn = NULL;
635	int error;
636
637	if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
638		return -EINVAL;
639
640	error = -ENOENT;
641	kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
642	if (!kn)
643		goto out;
644
645	error = -EINVAL;
646	if (kernfs_type(kn) != KERNFS_LINK)
647		goto out;
648	if (kn->symlink.target_kn->priv != targ)
649		goto out;
650
651	error = internal_change_owner(kn, kuid, kgid);
652
653out:
654	kernfs_put(kn);
655	return error;
656}
657
658/**
659 *	sysfs_file_change_owner - change owner of a sysfs file.
660 *	@kobj:	object.
661 *	@name:	name of the file to change.
662 *	@kuid:	new owner's kuid
663 *	@kgid:	new owner's kgid
664 *
665 * This function looks up the sysfs entry @name under @kobj and changes the
666 * ownership to @kuid/@kgid.
667 *
668 * Returns 0 on success or error code on failure.
669 */
670int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
671			    kgid_t kgid)
672{
673	struct kernfs_node *kn;
674	int error;
675
676	if (!name)
677		return -EINVAL;
678
679	if (!kobj->state_in_sysfs)
680		return -EINVAL;
681
682	kn = kernfs_find_and_get(kobj->sd, name);
683	if (!kn)
684		return -ENOENT;
685
686	error = internal_change_owner(kn, kuid, kgid);
687
688	kernfs_put(kn);
689
690	return error;
691}
692EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
693
694/**
695 *	sysfs_change_owner - change owner of the given object.
696 *	@kobj:	object.
697 *	@kuid:	new owner's kuid
698 *	@kgid:	new owner's kgid
699 *
700 * Change the owner of the default directory, files, groups, and attributes of
701 * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
702 * entries for a kobject are added by driver core. In summary,
703 * sysfs_change_owner() takes care of the default directory entry for @kobj,
704 * the default attributes associated with the ktype of @kobj and the default
705 * attributes associated with the ktype of @kobj.
706 * Additional properties not added by driver core have to be changed by the
707 * driver or subsystem which created them. This is similar to how
708 * driver/subsystem specific entries are removed.
709 *
710 * Returns 0 on success or error code on failure.
711 */
712int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
713{
714	int error;
715	const struct kobj_type *ktype;
716
717	if (!kobj->state_in_sysfs)
718		return -EINVAL;
719
720	/* Change the owner of the kobject itself. */
721	error = internal_change_owner(kobj->sd, kuid, kgid);
722	if (error)
723		return error;
724
725	ktype = get_ktype(kobj);
726	if (ktype) {
727		/*
728		 * Change owner of the default groups associated with the
729		 * ktype of @kobj.
730		 */
731		error = sysfs_groups_change_owner(kobj, ktype->default_groups,
732						  kuid, kgid);
733		if (error)
734			return error;
735	}
736
737	return 0;
738}
739EXPORT_SYMBOL_GPL(sysfs_change_owner);
740
741/**
742 *	sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
743 *	@buf:	start of PAGE_SIZE buffer.
744 *	@fmt:	format
745 *	@...:	optional arguments to @format
746 *
747 *
748 * Returns number of characters written to @buf.
749 */
750int sysfs_emit(char *buf, const char *fmt, ...)
751{
752	va_list args;
753	int len;
754
755	if (WARN(!buf || offset_in_page(buf),
756		 "invalid sysfs_emit: buf:%p\n", buf))
757		return 0;
758
759	va_start(args, fmt);
760	len = vscnprintf(buf, PAGE_SIZE, fmt, args);
761	va_end(args);
762
763	return len;
764}
765EXPORT_SYMBOL_GPL(sysfs_emit);
766
767/**
768 *	sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
769 *	@buf:	start of PAGE_SIZE buffer.
770 *	@at:	offset in @buf to start write in bytes
771 *		@at must be >= 0 && < PAGE_SIZE
772 *	@fmt:	format
773 *	@...:	optional arguments to @fmt
774 *
775 *
776 * Returns number of characters written starting at &@buf[@at].
777 */
778int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
779{
780	va_list args;
781	int len;
782
783	if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
784		 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
785		return 0;
786
787	va_start(args, fmt);
788	len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
789	va_end(args);
790
791	return len;
792}
793EXPORT_SYMBOL_GPL(sysfs_emit_at);
794
795/**
796 *	sysfs_bin_attr_simple_read - read callback to simply copy from memory.
797 *	@file:	attribute file which is being read.
798 *	@kobj:	object to which the attribute belongs.
799 *	@attr:	attribute descriptor.
800 *	@buf:	destination buffer.
801 *	@off:	offset in bytes from which to read.
802 *	@count:	maximum number of bytes to read.
803 *
804 * Simple ->read() callback for bin_attributes backed by a buffer in memory.
805 * The @private and @size members in struct bin_attribute must be set to the
806 * buffer's location and size before the bin_attribute is created in sysfs.
807 *
808 * Bounds check for @off and @count is done in sysfs_kf_bin_read().
809 * Negative value check for @off is done in vfs_setpos() and default_llseek().
810 *
811 * Returns number of bytes written to @buf.
812 */
813ssize_t sysfs_bin_attr_simple_read(struct file *file, struct kobject *kobj,
814				   const struct bin_attribute *attr, char *buf,
815				   loff_t off, size_t count)
816{
817	memcpy(buf, attr->private + off, count);
818	return count;
819}
820EXPORT_SYMBOL_GPL(sysfs_bin_attr_simple_read);