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1/*
2 * fs/sysfs/file.c - sysfs regular (text) file implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
7 *
8 * This file is released under the GPLv2.
9 *
10 * Please see Documentation/filesystems/sysfs.txt for more information.
11 */
12
13#include <linux/module.h>
14#include <linux/kobject.h>
15#include <linux/kallsyms.h>
16#include <linux/slab.h>
17#include <linux/fsnotify.h>
18#include <linux/namei.h>
19#include <linux/poll.h>
20#include <linux/list.h>
21#include <linux/mutex.h>
22#include <linux/limits.h>
23#include <asm/uaccess.h>
24
25#include "sysfs.h"
26
27/*
28 * There's one sysfs_buffer for each open file and one
29 * sysfs_open_dirent for each sysfs_dirent with one or more open
30 * files.
31 *
32 * filp->private_data points to sysfs_buffer and
33 * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open
34 * is protected by sysfs_open_dirent_lock.
35 */
36static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
37
38struct sysfs_open_dirent {
39 atomic_t refcnt;
40 atomic_t event;
41 wait_queue_head_t poll;
42 struct list_head buffers; /* goes through sysfs_buffer.list */
43};
44
45struct sysfs_buffer {
46 size_t count;
47 loff_t pos;
48 char * page;
49 const struct sysfs_ops * ops;
50 struct mutex mutex;
51 int needs_read_fill;
52 int event;
53 struct list_head list;
54};
55
56/**
57 * fill_read_buffer - allocate and fill buffer from object.
58 * @dentry: dentry pointer.
59 * @buffer: data buffer for file.
60 *
61 * Allocate @buffer->page, if it hasn't been already, then call the
62 * kobject's show() method to fill the buffer with this attribute's
63 * data.
64 * This is called only once, on the file's first read unless an error
65 * is returned.
66 */
67static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
68{
69 struct sysfs_dirent *attr_sd = dentry->d_fsdata;
70 struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
71 const struct sysfs_ops * ops = buffer->ops;
72 int ret = 0;
73 ssize_t count;
74
75 if (!buffer->page)
76 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
77 if (!buffer->page)
78 return -ENOMEM;
79
80 /* need attr_sd for attr and ops, its parent for kobj */
81 if (!sysfs_get_active(attr_sd))
82 return -ENODEV;
83
84 buffer->event = atomic_read(&attr_sd->s_attr.open->event);
85 count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
86
87 sysfs_put_active(attr_sd);
88
89 /*
90 * The code works fine with PAGE_SIZE return but it's likely to
91 * indicate truncated result or overflow in normal use cases.
92 */
93 if (count >= (ssize_t)PAGE_SIZE) {
94 print_symbol("fill_read_buffer: %s returned bad count\n",
95 (unsigned long)ops->show);
96 /* Try to struggle along */
97 count = PAGE_SIZE - 1;
98 }
99 if (count >= 0) {
100 buffer->needs_read_fill = 0;
101 buffer->count = count;
102 } else {
103 ret = count;
104 }
105 return ret;
106}
107
108/**
109 * sysfs_read_file - read an attribute.
110 * @file: file pointer.
111 * @buf: buffer to fill.
112 * @count: number of bytes to read.
113 * @ppos: starting offset in file.
114 *
115 * Userspace wants to read an attribute file. The attribute descriptor
116 * is in the file's ->d_fsdata. The target object is in the directory's
117 * ->d_fsdata.
118 *
119 * We call fill_read_buffer() to allocate and fill the buffer from the
120 * object's show() method exactly once (if the read is happening from
121 * the beginning of the file). That should fill the entire buffer with
122 * all the data the object has to offer for that attribute.
123 * We then call flush_read_buffer() to copy the buffer to userspace
124 * in the increments specified.
125 */
126
127static ssize_t
128sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
129{
130 struct sysfs_buffer * buffer = file->private_data;
131 ssize_t retval = 0;
132
133 mutex_lock(&buffer->mutex);
134 if (buffer->needs_read_fill || *ppos == 0) {
135 retval = fill_read_buffer(file->f_path.dentry,buffer);
136 if (retval)
137 goto out;
138 }
139 pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
140 __func__, count, *ppos, buffer->page);
141 retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
142 buffer->count);
143out:
144 mutex_unlock(&buffer->mutex);
145 return retval;
146}
147
148/**
149 * fill_write_buffer - copy buffer from userspace.
150 * @buffer: data buffer for file.
151 * @buf: data from user.
152 * @count: number of bytes in @userbuf.
153 *
154 * Allocate @buffer->page if it hasn't been already, then
155 * copy the user-supplied buffer into it.
156 */
157
158static int
159fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
160{
161 int error;
162
163 if (!buffer->page)
164 buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
165 if (!buffer->page)
166 return -ENOMEM;
167
168 if (count >= PAGE_SIZE)
169 count = PAGE_SIZE - 1;
170 error = copy_from_user(buffer->page,buf,count);
171 buffer->needs_read_fill = 1;
172 /* if buf is assumed to contain a string, terminate it by \0,
173 so e.g. sscanf() can scan the string easily */
174 buffer->page[count] = 0;
175 return error ? -EFAULT : count;
176}
177
178
179/**
180 * flush_write_buffer - push buffer to kobject.
181 * @dentry: dentry to the attribute
182 * @buffer: data buffer for file.
183 * @count: number of bytes
184 *
185 * Get the correct pointers for the kobject and the attribute we're
186 * dealing with, then call the store() method for the attribute,
187 * passing the buffer that we acquired in fill_write_buffer().
188 */
189
190static int
191flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
192{
193 struct sysfs_dirent *attr_sd = dentry->d_fsdata;
194 struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
195 const struct sysfs_ops * ops = buffer->ops;
196 int rc;
197
198 /* need attr_sd for attr and ops, its parent for kobj */
199 if (!sysfs_get_active(attr_sd))
200 return -ENODEV;
201
202 rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);
203
204 sysfs_put_active(attr_sd);
205
206 return rc;
207}
208
209
210/**
211 * sysfs_write_file - write an attribute.
212 * @file: file pointer
213 * @buf: data to write
214 * @count: number of bytes
215 * @ppos: starting offset
216 *
217 * Similar to sysfs_read_file(), though working in the opposite direction.
218 * We allocate and fill the data from the user in fill_write_buffer(),
219 * then push it to the kobject in flush_write_buffer().
220 * There is no easy way for us to know if userspace is only doing a partial
221 * write, so we don't support them. We expect the entire buffer to come
222 * on the first write.
223 * Hint: if you're writing a value, first read the file, modify only the
224 * the value you're changing, then write entire buffer back.
225 */
226
227static ssize_t
228sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
229{
230 struct sysfs_buffer * buffer = file->private_data;
231 ssize_t len;
232
233 mutex_lock(&buffer->mutex);
234 len = fill_write_buffer(buffer, buf, count);
235 if (len > 0)
236 len = flush_write_buffer(file->f_path.dentry, buffer, len);
237 if (len > 0)
238 *ppos += len;
239 mutex_unlock(&buffer->mutex);
240 return len;
241}
242
243/**
244 * sysfs_get_open_dirent - get or create sysfs_open_dirent
245 * @sd: target sysfs_dirent
246 * @buffer: sysfs_buffer for this instance of open
247 *
248 * If @sd->s_attr.open exists, increment its reference count;
249 * otherwise, create one. @buffer is chained to the buffers
250 * list.
251 *
252 * LOCKING:
253 * Kernel thread context (may sleep).
254 *
255 * RETURNS:
256 * 0 on success, -errno on failure.
257 */
258static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
259 struct sysfs_buffer *buffer)
260{
261 struct sysfs_open_dirent *od, *new_od = NULL;
262
263 retry:
264 spin_lock_irq(&sysfs_open_dirent_lock);
265
266 if (!sd->s_attr.open && new_od) {
267 sd->s_attr.open = new_od;
268 new_od = NULL;
269 }
270
271 od = sd->s_attr.open;
272 if (od) {
273 atomic_inc(&od->refcnt);
274 list_add_tail(&buffer->list, &od->buffers);
275 }
276
277 spin_unlock_irq(&sysfs_open_dirent_lock);
278
279 if (od) {
280 kfree(new_od);
281 return 0;
282 }
283
284 /* not there, initialize a new one and retry */
285 new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
286 if (!new_od)
287 return -ENOMEM;
288
289 atomic_set(&new_od->refcnt, 0);
290 atomic_set(&new_od->event, 1);
291 init_waitqueue_head(&new_od->poll);
292 INIT_LIST_HEAD(&new_od->buffers);
293 goto retry;
294}
295
296/**
297 * sysfs_put_open_dirent - put sysfs_open_dirent
298 * @sd: target sysfs_dirent
299 * @buffer: associated sysfs_buffer
300 *
301 * Put @sd->s_attr.open and unlink @buffer from the buffers list.
302 * If reference count reaches zero, disassociate and free it.
303 *
304 * LOCKING:
305 * None.
306 */
307static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
308 struct sysfs_buffer *buffer)
309{
310 struct sysfs_open_dirent *od = sd->s_attr.open;
311 unsigned long flags;
312
313 spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
314
315 list_del(&buffer->list);
316 if (atomic_dec_and_test(&od->refcnt))
317 sd->s_attr.open = NULL;
318 else
319 od = NULL;
320
321 spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
322
323 kfree(od);
324}
325
326static int sysfs_open_file(struct inode *inode, struct file *file)
327{
328 struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
329 struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
330 struct sysfs_buffer *buffer;
331 const struct sysfs_ops *ops;
332 int error = -EACCES;
333
334 /* need attr_sd for attr and ops, its parent for kobj */
335 if (!sysfs_get_active(attr_sd))
336 return -ENODEV;
337
338 /* every kobject with an attribute needs a ktype assigned */
339 if (kobj->ktype && kobj->ktype->sysfs_ops)
340 ops = kobj->ktype->sysfs_ops;
341 else {
342 WARN(1, KERN_ERR "missing sysfs attribute operations for "
343 "kobject: %s\n", kobject_name(kobj));
344 goto err_out;
345 }
346
347 /* File needs write support.
348 * The inode's perms must say it's ok,
349 * and we must have a store method.
350 */
351 if (file->f_mode & FMODE_WRITE) {
352 if (!(inode->i_mode & S_IWUGO) || !ops->store)
353 goto err_out;
354 }
355
356 /* File needs read support.
357 * The inode's perms must say it's ok, and we there
358 * must be a show method for it.
359 */
360 if (file->f_mode & FMODE_READ) {
361 if (!(inode->i_mode & S_IRUGO) || !ops->show)
362 goto err_out;
363 }
364
365 /* No error? Great, allocate a buffer for the file, and store it
366 * it in file->private_data for easy access.
367 */
368 error = -ENOMEM;
369 buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
370 if (!buffer)
371 goto err_out;
372
373 mutex_init(&buffer->mutex);
374 buffer->needs_read_fill = 1;
375 buffer->ops = ops;
376 file->private_data = buffer;
377
378 /* make sure we have open dirent struct */
379 error = sysfs_get_open_dirent(attr_sd, buffer);
380 if (error)
381 goto err_free;
382
383 /* open succeeded, put active references */
384 sysfs_put_active(attr_sd);
385 return 0;
386
387 err_free:
388 kfree(buffer);
389 err_out:
390 sysfs_put_active(attr_sd);
391 return error;
392}
393
394static int sysfs_release(struct inode *inode, struct file *filp)
395{
396 struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
397 struct sysfs_buffer *buffer = filp->private_data;
398
399 sysfs_put_open_dirent(sd, buffer);
400
401 if (buffer->page)
402 free_page((unsigned long)buffer->page);
403 kfree(buffer);
404
405 return 0;
406}
407
408/* Sysfs attribute files are pollable. The idea is that you read
409 * the content and then you use 'poll' or 'select' to wait for
410 * the content to change. When the content changes (assuming the
411 * manager for the kobject supports notification), poll will
412 * return POLLERR|POLLPRI, and select will return the fd whether
413 * it is waiting for read, write, or exceptions.
414 * Once poll/select indicates that the value has changed, you
415 * need to close and re-open the file, or seek to 0 and read again.
416 * Reminder: this only works for attributes which actively support
417 * it, and it is not possible to test an attribute from userspace
418 * to see if it supports poll (Neither 'poll' nor 'select' return
419 * an appropriate error code). When in doubt, set a suitable timeout value.
420 */
421static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
422{
423 struct sysfs_buffer * buffer = filp->private_data;
424 struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
425 struct sysfs_open_dirent *od = attr_sd->s_attr.open;
426
427 /* need parent for the kobj, grab both */
428 if (!sysfs_get_active(attr_sd))
429 goto trigger;
430
431 poll_wait(filp, &od->poll, wait);
432
433 sysfs_put_active(attr_sd);
434
435 if (buffer->event != atomic_read(&od->event))
436 goto trigger;
437
438 return DEFAULT_POLLMASK;
439
440 trigger:
441 buffer->needs_read_fill = 1;
442 return DEFAULT_POLLMASK|POLLERR|POLLPRI;
443}
444
445void sysfs_notify_dirent(struct sysfs_dirent *sd)
446{
447 struct sysfs_open_dirent *od;
448 unsigned long flags;
449
450 spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
451
452 od = sd->s_attr.open;
453 if (od) {
454 atomic_inc(&od->event);
455 wake_up_interruptible(&od->poll);
456 }
457
458 spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
459}
460EXPORT_SYMBOL_GPL(sysfs_notify_dirent);
461
462void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
463{
464 struct sysfs_dirent *sd = k->sd;
465
466 mutex_lock(&sysfs_mutex);
467
468 if (sd && dir)
469 /* Only directories are tagged, so no need to pass
470 * a tag explicitly.
471 */
472 sd = sysfs_find_dirent(sd, NULL, dir);
473 if (sd && attr)
474 sd = sysfs_find_dirent(sd, NULL, attr);
475 if (sd)
476 sysfs_notify_dirent(sd);
477
478 mutex_unlock(&sysfs_mutex);
479}
480EXPORT_SYMBOL_GPL(sysfs_notify);
481
482const struct file_operations sysfs_file_operations = {
483 .read = sysfs_read_file,
484 .write = sysfs_write_file,
485 .llseek = generic_file_llseek,
486 .open = sysfs_open_file,
487 .release = sysfs_release,
488 .poll = sysfs_poll,
489};
490
491int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
492 const struct attribute *attr, int type, mode_t amode)
493{
494 umode_t mode = (amode & S_IALLUGO) | S_IFREG;
495 struct sysfs_addrm_cxt acxt;
496 struct sysfs_dirent *sd;
497 int rc;
498
499 sd = sysfs_new_dirent(attr->name, mode, type);
500 if (!sd)
501 return -ENOMEM;
502 sd->s_attr.attr = (void *)attr;
503 sysfs_dirent_init_lockdep(sd);
504
505 sysfs_addrm_start(&acxt, dir_sd);
506 rc = sysfs_add_one(&acxt, sd);
507 sysfs_addrm_finish(&acxt);
508
509 if (rc)
510 sysfs_put(sd);
511
512 return rc;
513}
514
515
516int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
517 int type)
518{
519 return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
520}
521
522
523/**
524 * sysfs_create_file - create an attribute file for an object.
525 * @kobj: object we're creating for.
526 * @attr: attribute descriptor.
527 */
528
529int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
530{
531 BUG_ON(!kobj || !kobj->sd || !attr);
532
533 return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
534
535}
536
537int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
538{
539 int err = 0;
540 int i;
541
542 for (i = 0; ptr[i] && !err; i++)
543 err = sysfs_create_file(kobj, ptr[i]);
544 if (err)
545 while (--i >= 0)
546 sysfs_remove_file(kobj, ptr[i]);
547 return err;
548}
549
550/**
551 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
552 * @kobj: object we're acting for.
553 * @attr: attribute descriptor.
554 * @group: group name.
555 */
556int sysfs_add_file_to_group(struct kobject *kobj,
557 const struct attribute *attr, const char *group)
558{
559 struct sysfs_dirent *dir_sd;
560 int error;
561
562 if (group)
563 dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
564 else
565 dir_sd = sysfs_get(kobj->sd);
566
567 if (!dir_sd)
568 return -ENOENT;
569
570 error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
571 sysfs_put(dir_sd);
572
573 return error;
574}
575EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
576
577/**
578 * sysfs_chmod_file - update the modified mode value on an object attribute.
579 * @kobj: object we're acting for.
580 * @attr: attribute descriptor.
581 * @mode: file permissions.
582 *
583 */
584int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
585 mode_t mode)
586{
587 struct sysfs_dirent *sd;
588 struct iattr newattrs;
589 int rc;
590
591 mutex_lock(&sysfs_mutex);
592
593 rc = -ENOENT;
594 sd = sysfs_find_dirent(kobj->sd, NULL, attr->name);
595 if (!sd)
596 goto out;
597
598 newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
599 newattrs.ia_valid = ATTR_MODE;
600 rc = sysfs_sd_setattr(sd, &newattrs);
601
602 out:
603 mutex_unlock(&sysfs_mutex);
604 return rc;
605}
606EXPORT_SYMBOL_GPL(sysfs_chmod_file);
607
608
609/**
610 * sysfs_remove_file - remove an object attribute.
611 * @kobj: object we're acting for.
612 * @attr: attribute descriptor.
613 *
614 * Hash the attribute name and kill the victim.
615 */
616
617void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
618{
619 sysfs_hash_and_remove(kobj->sd, NULL, attr->name);
620}
621
622void sysfs_remove_files(struct kobject * kobj, const struct attribute **ptr)
623{
624 int i;
625 for (i = 0; ptr[i]; i++)
626 sysfs_remove_file(kobj, ptr[i]);
627}
628
629/**
630 * sysfs_remove_file_from_group - remove an attribute file from a group.
631 * @kobj: object we're acting for.
632 * @attr: attribute descriptor.
633 * @group: group name.
634 */
635void sysfs_remove_file_from_group(struct kobject *kobj,
636 const struct attribute *attr, const char *group)
637{
638 struct sysfs_dirent *dir_sd;
639
640 if (group)
641 dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
642 else
643 dir_sd = sysfs_get(kobj->sd);
644 if (dir_sd) {
645 sysfs_hash_and_remove(dir_sd, NULL, attr->name);
646 sysfs_put(dir_sd);
647 }
648}
649EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
650
651struct sysfs_schedule_callback_struct {
652 struct list_head workq_list;
653 struct kobject *kobj;
654 void (*func)(void *);
655 void *data;
656 struct module *owner;
657 struct work_struct work;
658};
659
660static struct workqueue_struct *sysfs_workqueue;
661static DEFINE_MUTEX(sysfs_workq_mutex);
662static LIST_HEAD(sysfs_workq);
663static void sysfs_schedule_callback_work(struct work_struct *work)
664{
665 struct sysfs_schedule_callback_struct *ss = container_of(work,
666 struct sysfs_schedule_callback_struct, work);
667
668 (ss->func)(ss->data);
669 kobject_put(ss->kobj);
670 module_put(ss->owner);
671 mutex_lock(&sysfs_workq_mutex);
672 list_del(&ss->workq_list);
673 mutex_unlock(&sysfs_workq_mutex);
674 kfree(ss);
675}
676
677/**
678 * sysfs_schedule_callback - helper to schedule a callback for a kobject
679 * @kobj: object we're acting for.
680 * @func: callback function to invoke later.
681 * @data: argument to pass to @func.
682 * @owner: module owning the callback code
683 *
684 * sysfs attribute methods must not unregister themselves or their parent
685 * kobject (which would amount to the same thing). Attempts to do so will
686 * deadlock, since unregistration is mutually exclusive with driver
687 * callbacks.
688 *
689 * Instead methods can call this routine, which will attempt to allocate
690 * and schedule a workqueue request to call back @func with @data as its
691 * argument in the workqueue's process context. @kobj will be pinned
692 * until @func returns.
693 *
694 * Returns 0 if the request was submitted, -ENOMEM if storage could not
695 * be allocated, -ENODEV if a reference to @owner isn't available,
696 * -EAGAIN if a callback has already been scheduled for @kobj.
697 */
698int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
699 void *data, struct module *owner)
700{
701 struct sysfs_schedule_callback_struct *ss, *tmp;
702
703 if (!try_module_get(owner))
704 return -ENODEV;
705
706 mutex_lock(&sysfs_workq_mutex);
707 list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
708 if (ss->kobj == kobj) {
709 module_put(owner);
710 mutex_unlock(&sysfs_workq_mutex);
711 return -EAGAIN;
712 }
713 mutex_unlock(&sysfs_workq_mutex);
714
715 if (sysfs_workqueue == NULL) {
716 sysfs_workqueue = create_singlethread_workqueue("sysfsd");
717 if (sysfs_workqueue == NULL) {
718 module_put(owner);
719 return -ENOMEM;
720 }
721 }
722
723 ss = kmalloc(sizeof(*ss), GFP_KERNEL);
724 if (!ss) {
725 module_put(owner);
726 return -ENOMEM;
727 }
728 kobject_get(kobj);
729 ss->kobj = kobj;
730 ss->func = func;
731 ss->data = data;
732 ss->owner = owner;
733 INIT_WORK(&ss->work, sysfs_schedule_callback_work);
734 INIT_LIST_HEAD(&ss->workq_list);
735 mutex_lock(&sysfs_workq_mutex);
736 list_add_tail(&ss->workq_list, &sysfs_workq);
737 mutex_unlock(&sysfs_workq_mutex);
738 queue_work(sysfs_workqueue, &ss->work);
739 return 0;
740}
741EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
742
743
744EXPORT_SYMBOL_GPL(sysfs_create_file);
745EXPORT_SYMBOL_GPL(sysfs_remove_file);
746EXPORT_SYMBOL_GPL(sysfs_remove_files);
747EXPORT_SYMBOL_GPL(sysfs_create_files);
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 && !battr->read_new)
95 return -EIO;
96
97 if (battr->read_new)
98 return battr->read_new(of->file, kobj, battr, buf, pos, count);
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 && !battr->write_new)
159 return -EIO;
160
161 if (battr->write_new)
162 return battr->write_new(of->file, kobj, battr, buf, pos, count);
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 struct bin_attribute *battr = of->kn->priv;
171 struct kobject *kobj = of->kn->parent->priv;
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 struct bin_attribute *battr = of->kn->priv;
180 struct kobject *kobj = of->kn->parent->priv;
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 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->read && battr->read_new)
333 return -EINVAL;
334
335 if (battr->write && battr->write_new)
336 return -EINVAL;
337
338 if (battr->mmap)
339 ops = &sysfs_bin_kfops_mmap;
340 else if ((battr->read || battr->read_new) && (battr->write || battr->write_new))
341 ops = &sysfs_bin_kfops_rw;
342 else if (battr->read || battr->read_new)
343 ops = &sysfs_bin_kfops_ro;
344 else if (battr->write || battr->write_new)
345 ops = &sysfs_bin_kfops_wo;
346 else
347 ops = &sysfs_file_kfops_empty;
348
349#ifdef CONFIG_DEBUG_LOCK_ALLOC
350 if (!attr->ignore_lockdep)
351 key = attr->key ?: (struct lock_class_key *)&attr->skey;
352#endif
353
354 kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
355 size, ops, (void *)attr, ns, key);
356 if (IS_ERR(kn)) {
357 if (PTR_ERR(kn) == -EEXIST)
358 sysfs_warn_dup(parent, attr->name);
359 return PTR_ERR(kn);
360 }
361 return 0;
362}
363
364/**
365 * sysfs_create_file_ns - create an attribute file for an object with custom ns
366 * @kobj: object we're creating for
367 * @attr: attribute descriptor
368 * @ns: namespace the new file should belong to
369 */
370int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
371 const void *ns)
372{
373 kuid_t uid;
374 kgid_t gid;
375
376 if (WARN_ON(!kobj || !kobj->sd || !attr))
377 return -EINVAL;
378
379 kobject_get_ownership(kobj, &uid, &gid);
380 return sysfs_add_file_mode_ns(kobj->sd, attr, attr->mode, uid, gid, ns);
381}
382EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
383
384int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
385{
386 int err = 0;
387 int i;
388
389 for (i = 0; ptr[i] && !err; i++)
390 err = sysfs_create_file(kobj, ptr[i]);
391 if (err)
392 while (--i >= 0)
393 sysfs_remove_file(kobj, ptr[i]);
394 return err;
395}
396EXPORT_SYMBOL_GPL(sysfs_create_files);
397
398/**
399 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
400 * @kobj: object we're acting for.
401 * @attr: attribute descriptor.
402 * @group: group name.
403 */
404int sysfs_add_file_to_group(struct kobject *kobj,
405 const struct attribute *attr, const char *group)
406{
407 struct kernfs_node *parent;
408 kuid_t uid;
409 kgid_t gid;
410 int error;
411
412 if (group) {
413 parent = kernfs_find_and_get(kobj->sd, group);
414 } else {
415 parent = kobj->sd;
416 kernfs_get(parent);
417 }
418
419 if (!parent)
420 return -ENOENT;
421
422 kobject_get_ownership(kobj, &uid, &gid);
423 error = sysfs_add_file_mode_ns(parent, attr, attr->mode, uid, gid,
424 NULL);
425 kernfs_put(parent);
426
427 return error;
428}
429EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
430
431/**
432 * sysfs_chmod_file - update the modified mode value on an object attribute.
433 * @kobj: object we're acting for.
434 * @attr: attribute descriptor.
435 * @mode: file permissions.
436 *
437 */
438int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
439 umode_t mode)
440{
441 struct kernfs_node *kn;
442 struct iattr newattrs;
443 int rc;
444
445 kn = kernfs_find_and_get(kobj->sd, attr->name);
446 if (!kn)
447 return -ENOENT;
448
449 newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
450 newattrs.ia_valid = ATTR_MODE;
451
452 rc = kernfs_setattr(kn, &newattrs);
453
454 kernfs_put(kn);
455 return rc;
456}
457EXPORT_SYMBOL_GPL(sysfs_chmod_file);
458
459/**
460 * sysfs_break_active_protection - break "active" protection
461 * @kobj: The kernel object @attr is associated with.
462 * @attr: The attribute to break the "active" protection for.
463 *
464 * With sysfs, just like kernfs, deletion of an attribute is postponed until
465 * all active .show() and .store() callbacks have finished unless this function
466 * is called. Hence this function is useful in methods that implement self
467 * deletion.
468 */
469struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
470 const struct attribute *attr)
471{
472 struct kernfs_node *kn;
473
474 kobject_get(kobj);
475 kn = kernfs_find_and_get(kobj->sd, attr->name);
476 if (kn)
477 kernfs_break_active_protection(kn);
478 else
479 kobject_put(kobj);
480 return kn;
481}
482EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
483
484/**
485 * sysfs_unbreak_active_protection - restore "active" protection
486 * @kn: Pointer returned by sysfs_break_active_protection().
487 *
488 * Undo the effects of sysfs_break_active_protection(). Since this function
489 * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
490 * argument passed to sysfs_break_active_protection() that attribute may have
491 * been removed between the sysfs_break_active_protection() and
492 * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
493 * this function has returned.
494 */
495void sysfs_unbreak_active_protection(struct kernfs_node *kn)
496{
497 struct kobject *kobj = kn->parent->priv;
498
499 kernfs_unbreak_active_protection(kn);
500 kernfs_put(kn);
501 kobject_put(kobj);
502}
503EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
504
505/**
506 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
507 * @kobj: object we're acting for
508 * @attr: attribute descriptor
509 * @ns: namespace tag of the file to remove
510 *
511 * Hash the attribute name and namespace tag and kill the victim.
512 */
513void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
514 const void *ns)
515{
516 struct kernfs_node *parent = kobj->sd;
517
518 kernfs_remove_by_name_ns(parent, attr->name, ns);
519}
520EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
521
522/**
523 * sysfs_remove_file_self - remove an object attribute from its own method
524 * @kobj: object we're acting for
525 * @attr: attribute descriptor
526 *
527 * See kernfs_remove_self() for details.
528 */
529bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
530{
531 struct kernfs_node *parent = kobj->sd;
532 struct kernfs_node *kn;
533 bool ret;
534
535 kn = kernfs_find_and_get(parent, attr->name);
536 if (WARN_ON_ONCE(!kn))
537 return false;
538
539 ret = kernfs_remove_self(kn);
540
541 kernfs_put(kn);
542 return ret;
543}
544EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
545
546void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
547{
548 int i;
549
550 for (i = 0; ptr[i]; i++)
551 sysfs_remove_file(kobj, ptr[i]);
552}
553EXPORT_SYMBOL_GPL(sysfs_remove_files);
554
555/**
556 * sysfs_remove_file_from_group - remove an attribute file from a group.
557 * @kobj: object we're acting for.
558 * @attr: attribute descriptor.
559 * @group: group name.
560 */
561void sysfs_remove_file_from_group(struct kobject *kobj,
562 const struct attribute *attr, const char *group)
563{
564 struct kernfs_node *parent;
565
566 if (group) {
567 parent = kernfs_find_and_get(kobj->sd, group);
568 } else {
569 parent = kobj->sd;
570 kernfs_get(parent);
571 }
572
573 if (parent) {
574 kernfs_remove_by_name(parent, attr->name);
575 kernfs_put(parent);
576 }
577}
578EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
579
580/**
581 * sysfs_create_bin_file - create binary file for object.
582 * @kobj: object.
583 * @attr: attribute descriptor.
584 */
585int sysfs_create_bin_file(struct kobject *kobj,
586 const struct bin_attribute *attr)
587{
588 kuid_t uid;
589 kgid_t gid;
590
591 if (WARN_ON(!kobj || !kobj->sd || !attr))
592 return -EINVAL;
593
594 kobject_get_ownership(kobj, &uid, &gid);
595 return sysfs_add_bin_file_mode_ns(kobj->sd, attr, attr->attr.mode,
596 attr->size, uid, gid, NULL);
597}
598EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
599
600/**
601 * sysfs_remove_bin_file - remove binary file for object.
602 * @kobj: object.
603 * @attr: attribute descriptor.
604 */
605void sysfs_remove_bin_file(struct kobject *kobj,
606 const struct bin_attribute *attr)
607{
608 kernfs_remove_by_name(kobj->sd, attr->attr.name);
609}
610EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
611
612static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
613 kgid_t kgid)
614{
615 struct iattr newattrs = {
616 .ia_valid = ATTR_UID | ATTR_GID,
617 .ia_uid = kuid,
618 .ia_gid = kgid,
619 };
620 return kernfs_setattr(kn, &newattrs);
621}
622
623/**
624 * sysfs_link_change_owner - change owner of a sysfs file.
625 * @kobj: object of the kernfs_node the symlink is located in.
626 * @targ: object of the kernfs_node the symlink points to.
627 * @name: name of the link.
628 * @kuid: new owner's kuid
629 * @kgid: new owner's kgid
630 *
631 * This function looks up the sysfs symlink entry @name under @kobj and changes
632 * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
633 * @targ.
634 *
635 * Returns 0 on success or error code on failure.
636 */
637int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
638 const char *name, kuid_t kuid, kgid_t kgid)
639{
640 struct kernfs_node *kn = NULL;
641 int error;
642
643 if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
644 return -EINVAL;
645
646 error = -ENOENT;
647 kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
648 if (!kn)
649 goto out;
650
651 error = -EINVAL;
652 if (kernfs_type(kn) != KERNFS_LINK)
653 goto out;
654 if (kn->symlink.target_kn->priv != targ)
655 goto out;
656
657 error = internal_change_owner(kn, kuid, kgid);
658
659out:
660 kernfs_put(kn);
661 return error;
662}
663
664/**
665 * sysfs_file_change_owner - change owner of a sysfs file.
666 * @kobj: object.
667 * @name: name of the file to change.
668 * @kuid: new owner's kuid
669 * @kgid: new owner's kgid
670 *
671 * This function looks up the sysfs entry @name under @kobj and changes the
672 * ownership to @kuid/@kgid.
673 *
674 * Returns 0 on success or error code on failure.
675 */
676int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
677 kgid_t kgid)
678{
679 struct kernfs_node *kn;
680 int error;
681
682 if (!name)
683 return -EINVAL;
684
685 if (!kobj->state_in_sysfs)
686 return -EINVAL;
687
688 kn = kernfs_find_and_get(kobj->sd, name);
689 if (!kn)
690 return -ENOENT;
691
692 error = internal_change_owner(kn, kuid, kgid);
693
694 kernfs_put(kn);
695
696 return error;
697}
698EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
699
700/**
701 * sysfs_change_owner - change owner of the given object.
702 * @kobj: object.
703 * @kuid: new owner's kuid
704 * @kgid: new owner's kgid
705 *
706 * Change the owner of the default directory, files, groups, and attributes of
707 * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
708 * entries for a kobject are added by driver core. In summary,
709 * sysfs_change_owner() takes care of the default directory entry for @kobj,
710 * the default attributes associated with the ktype of @kobj and the default
711 * attributes associated with the ktype of @kobj.
712 * Additional properties not added by driver core have to be changed by the
713 * driver or subsystem which created them. This is similar to how
714 * driver/subsystem specific entries are removed.
715 *
716 * Returns 0 on success or error code on failure.
717 */
718int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
719{
720 int error;
721 const struct kobj_type *ktype;
722
723 if (!kobj->state_in_sysfs)
724 return -EINVAL;
725
726 /* Change the owner of the kobject itself. */
727 error = internal_change_owner(kobj->sd, kuid, kgid);
728 if (error)
729 return error;
730
731 ktype = get_ktype(kobj);
732 if (ktype) {
733 /*
734 * Change owner of the default groups associated with the
735 * ktype of @kobj.
736 */
737 error = sysfs_groups_change_owner(kobj, ktype->default_groups,
738 kuid, kgid);
739 if (error)
740 return error;
741 }
742
743 return 0;
744}
745EXPORT_SYMBOL_GPL(sysfs_change_owner);
746
747/**
748 * sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
749 * @buf: start of PAGE_SIZE buffer.
750 * @fmt: format
751 * @...: optional arguments to @format
752 *
753 *
754 * Returns number of characters written to @buf.
755 */
756int sysfs_emit(char *buf, const char *fmt, ...)
757{
758 va_list args;
759 int len;
760
761 if (WARN(!buf || offset_in_page(buf),
762 "invalid sysfs_emit: buf:%p\n", buf))
763 return 0;
764
765 va_start(args, fmt);
766 len = vscnprintf(buf, PAGE_SIZE, fmt, args);
767 va_end(args);
768
769 return len;
770}
771EXPORT_SYMBOL_GPL(sysfs_emit);
772
773/**
774 * sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
775 * @buf: start of PAGE_SIZE buffer.
776 * @at: offset in @buf to start write in bytes
777 * @at must be >= 0 && < PAGE_SIZE
778 * @fmt: format
779 * @...: optional arguments to @fmt
780 *
781 *
782 * Returns number of characters written starting at &@buf[@at].
783 */
784int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
785{
786 va_list args;
787 int len;
788
789 if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
790 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
791 return 0;
792
793 va_start(args, fmt);
794 len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
795 va_end(args);
796
797 return len;
798}
799EXPORT_SYMBOL_GPL(sysfs_emit_at);
800
801/**
802 * sysfs_bin_attr_simple_read - read callback to simply copy from memory.
803 * @file: attribute file which is being read.
804 * @kobj: object to which the attribute belongs.
805 * @attr: attribute descriptor.
806 * @buf: destination buffer.
807 * @off: offset in bytes from which to read.
808 * @count: maximum number of bytes to read.
809 *
810 * Simple ->read() callback for bin_attributes backed by a buffer in memory.
811 * The @private and @size members in struct bin_attribute must be set to the
812 * buffer's location and size before the bin_attribute is created in sysfs.
813 *
814 * Bounds check for @off and @count is done in sysfs_kf_bin_read().
815 * Negative value check for @off is done in vfs_setpos() and default_llseek().
816 *
817 * Returns number of bytes written to @buf.
818 */
819ssize_t sysfs_bin_attr_simple_read(struct file *file, struct kobject *kobj,
820 struct bin_attribute *attr, char *buf,
821 loff_t off, size_t count)
822{
823 memcpy(buf, attr->private + off, count);
824 return count;
825}
826EXPORT_SYMBOL_GPL(sysfs_bin_attr_simple_read);