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Version: [ 2.6.11.8 ] [ 2.6.25 ] [ 2.6.25.8 ] [ 2.6.31.13 ] Architecture: [ i386 ]
  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/namei.h>
 17 #include <linux/poll.h>
 18 #include <linux/list.h>
 19 #include <linux/mutex.h>
 20 #include <asm/uaccess.h>
 21 
 22 #include "sysfs.h"
 23 
 24 /*
 25  * There's one sysfs_buffer for each open file and one
 26  * sysfs_open_dirent for each sysfs_dirent with one or more open
 27  * files.
 28  *
 29  * filp->private_data points to sysfs_buffer and
 30  * sysfs_dirent->s_attr.open points to sysfs_open_dirent.  s_attr.open
 31  * is protected by sysfs_open_dirent_lock.
 32  */
 33 static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
 34 
 35 struct sysfs_open_dirent {
 36         atomic_t                refcnt;
 37         atomic_t                event;
 38         wait_queue_head_t       poll;
 39         struct list_head        buffers; /* goes through sysfs_buffer.list */
 40 };
 41 
 42 struct sysfs_buffer {
 43         size_t                  count;
 44         loff_t                  pos;
 45         char                    * page;
 46         struct sysfs_ops        * ops;
 47         struct mutex            mutex;
 48         int                     needs_read_fill;
 49         int                     event;
 50         struct list_head        list;
 51 };
 52 
 53 /**
 54  *      fill_read_buffer - allocate and fill buffer from object.
 55  *      @dentry:        dentry pointer.
 56  *      @buffer:        data buffer for file.
 57  *
 58  *      Allocate @buffer->page, if it hasn't been already, then call the
 59  *      kobject's show() method to fill the buffer with this attribute's 
 60  *      data. 
 61  *      This is called only once, on the file's first read unless an error
 62  *      is returned.
 63  */
 64 static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
 65 {
 66         struct sysfs_dirent *attr_sd = dentry->d_fsdata;
 67         struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
 68         struct sysfs_ops * ops = buffer->ops;
 69         int ret = 0;
 70         ssize_t count;
 71 
 72         if (!buffer->page)
 73                 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
 74         if (!buffer->page)
 75                 return -ENOMEM;
 76 
 77         /* need attr_sd for attr and ops, its parent for kobj */
 78         if (!sysfs_get_active_two(attr_sd))
 79                 return -ENODEV;
 80 
 81         buffer->event = atomic_read(&attr_sd->s_attr.open->event);
 82         count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
 83 
 84         sysfs_put_active_two(attr_sd);
 85 
 86         /*
 87          * The code works fine with PAGE_SIZE return but it's likely to
 88          * indicate truncated result or overflow in normal use cases.
 89          */
 90         if (count >= (ssize_t)PAGE_SIZE) {
 91                 print_symbol("fill_read_buffer: %s returned bad count\n",
 92                         (unsigned long)ops->show);
 93                 /* Try to struggle along */
 94                 count = PAGE_SIZE - 1;
 95         }
 96         if (count >= 0) {
 97                 buffer->needs_read_fill = 0;
 98                 buffer->count = count;
 99         } else {
100                 ret = count;
101         }
102         return ret;
103 }
104 
105 /**
106  *      sysfs_read_file - read an attribute. 
107  *      @file:  file pointer.
108  *      @buf:   buffer to fill.
109  *      @count: number of bytes to read.
110  *      @ppos:  starting offset in file.
111  *
112  *      Userspace wants to read an attribute file. The attribute descriptor
113  *      is in the file's ->d_fsdata. The target object is in the directory's
114  *      ->d_fsdata.
115  *
116  *      We call fill_read_buffer() to allocate and fill the buffer from the
117  *      object's show() method exactly once (if the read is happening from
118  *      the beginning of the file). That should fill the entire buffer with
119  *      all the data the object has to offer for that attribute.
120  *      We then call flush_read_buffer() to copy the buffer to userspace
121  *      in the increments specified.
122  */
123 
124 static ssize_t
125 sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
126 {
127         struct sysfs_buffer * buffer = file->private_data;
128         ssize_t retval = 0;
129 
130         mutex_lock(&buffer->mutex);
131         if (buffer->needs_read_fill) {
132                 retval = fill_read_buffer(file->f_path.dentry,buffer);
133                 if (retval)
134                         goto out;
135         }
136         pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
137                  __FUNCTION__, count, *ppos, buffer->page);
138         retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
139                                          buffer->count);
140 out:
141         mutex_unlock(&buffer->mutex);
142         return retval;
143 }
144 
145 /**
146  *      fill_write_buffer - copy buffer from userspace.
147  *      @buffer:        data buffer for file.
148  *      @buf:           data from user.
149  *      @count:         number of bytes in @userbuf.
150  *
151  *      Allocate @buffer->page if it hasn't been already, then
152  *      copy the user-supplied buffer into it.
153  */
154 
155 static int 
156 fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
157 {
158         int error;
159 
160         if (!buffer->page)
161                 buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
162         if (!buffer->page)
163                 return -ENOMEM;
164 
165         if (count >= PAGE_SIZE)
166                 count = PAGE_SIZE - 1;
167         error = copy_from_user(buffer->page,buf,count);
168         buffer->needs_read_fill = 1;
169         /* if buf is assumed to contain a string, terminate it by \0,
170            so e.g. sscanf() can scan the string easily */
171         buffer->page[count] = 0;
172         return error ? -EFAULT : count;
173 }
174 
175 
176 /**
177  *      flush_write_buffer - push buffer to kobject.
178  *      @dentry:        dentry to the attribute
179  *      @buffer:        data buffer for file.
180  *      @count:         number of bytes
181  *
182  *      Get the correct pointers for the kobject and the attribute we're
183  *      dealing with, then call the store() method for the attribute, 
184  *      passing the buffer that we acquired in fill_write_buffer().
185  */
186 
187 static int
188 flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
189 {
190         struct sysfs_dirent *attr_sd = dentry->d_fsdata;
191         struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
192         struct sysfs_ops * ops = buffer->ops;
193         int rc;
194 
195         /* need attr_sd for attr and ops, its parent for kobj */
196         if (!sysfs_get_active_two(attr_sd))
197                 return -ENODEV;
198 
199         rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);
200 
201         sysfs_put_active_two(attr_sd);
202 
203         return rc;
204 }
205 
206 
207 /**
208  *      sysfs_write_file - write an attribute.
209  *      @file:  file pointer
210  *      @buf:   data to write
211  *      @count: number of bytes
212  *      @ppos:  starting offset
213  *
214  *      Similar to sysfs_read_file(), though working in the opposite direction.
215  *      We allocate and fill the data from the user in fill_write_buffer(),
216  *      then push it to the kobject in flush_write_buffer().
217  *      There is no easy way for us to know if userspace is only doing a partial
218  *      write, so we don't support them. We expect the entire buffer to come
219  *      on the first write. 
220  *      Hint: if you're writing a value, first read the file, modify only the
221  *      the value you're changing, then write entire buffer back. 
222  */
223 
224 static ssize_t
225 sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
226 {
227         struct sysfs_buffer * buffer = file->private_data;
228         ssize_t len;
229 
230         mutex_lock(&buffer->mutex);
231         len = fill_write_buffer(buffer, buf, count);
232         if (len > 0)
233                 len = flush_write_buffer(file->f_path.dentry, buffer, len);
234         if (len > 0)
235                 *ppos += len;
236         mutex_unlock(&buffer->mutex);
237         return len;
238 }
239 
240 /**
241  *      sysfs_get_open_dirent - get or create sysfs_open_dirent
242  *      @sd: target sysfs_dirent
243  *      @buffer: sysfs_buffer for this instance of open
244  *
245  *      If @sd->s_attr.open exists, increment its reference count;
246  *      otherwise, create one.  @buffer is chained to the buffers
247  *      list.
248  *
249  *      LOCKING:
250  *      Kernel thread context (may sleep).
251  *
252  *      RETURNS:
253  *      0 on success, -errno on failure.
254  */
255 static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
256                                  struct sysfs_buffer *buffer)
257 {
258         struct sysfs_open_dirent *od, *new_od = NULL;
259 
260  retry:
261         spin_lock(&sysfs_open_dirent_lock);
262 
263         if (!sd->s_attr.open && new_od) {
264                 sd->s_attr.open = new_od;
265                 new_od = NULL;
266         }
267 
268         od = sd->s_attr.open;
269         if (od) {
270                 atomic_inc(&od->refcnt);
271                 list_add_tail(&buffer->list, &od->buffers);
272         }
273 
274         spin_unlock(&sysfs_open_dirent_lock);
275 
276         if (od) {
277                 kfree(new_od);
278                 return 0;
279         }
280 
281         /* not there, initialize a new one and retry */
282         new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
283         if (!new_od)
284                 return -ENOMEM;
285 
286         atomic_set(&new_od->refcnt, 0);
287         atomic_set(&new_od->event, 1);
288         init_waitqueue_head(&new_od->poll);
289         INIT_LIST_HEAD(&new_od->buffers);
290         goto retry;
291 }
292 
293 /**
294  *      sysfs_put_open_dirent - put sysfs_open_dirent
295  *      @sd: target sysfs_dirent
296  *      @buffer: associated sysfs_buffer
297  *
298  *      Put @sd->s_attr.open and unlink @buffer from the buffers list.
299  *      If reference count reaches zero, disassociate and free it.
300  *
301  *      LOCKING:
302  *      None.
303  */
304 static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
305                                   struct sysfs_buffer *buffer)
306 {
307         struct sysfs_open_dirent *od = sd->s_attr.open;
308 
309         spin_lock(&sysfs_open_dirent_lock);
310 
311         list_del(&buffer->list);
312         if (atomic_dec_and_test(&od->refcnt))
313                 sd->s_attr.open = NULL;
314         else
315                 od = NULL;
316 
317         spin_unlock(&sysfs_open_dirent_lock);
318 
319         kfree(od);
320 }
321 
322 static int sysfs_open_file(struct inode *inode, struct file *file)
323 {
324         struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
325         struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
326         struct sysfs_buffer *buffer;
327         struct sysfs_ops *ops;
328         int error = -EACCES;
329 
330         /* need attr_sd for attr and ops, its parent for kobj */
331         if (!sysfs_get_active_two(attr_sd))
332                 return -ENODEV;
333 
334         /* every kobject with an attribute needs a ktype assigned */
335         if (kobj->ktype && kobj->ktype->sysfs_ops)
336                 ops = kobj->ktype->sysfs_ops;
337         else {
338                 printk(KERN_ERR "missing sysfs attribute operations for "
339                        "kobject: %s\n", kobject_name(kobj));
340                 WARN_ON(1);
341                 goto err_out;
342         }
343 
344         /* File needs write support.
345          * The inode's perms must say it's ok, 
346          * and we must have a store method.
347          */
348         if (file->f_mode & FMODE_WRITE) {
349                 if (!(inode->i_mode & S_IWUGO) || !ops->store)
350                         goto err_out;
351         }
352 
353         /* File needs read support.
354          * The inode's perms must say it's ok, and we there
355          * must be a show method for it.
356          */
357         if (file->f_mode & FMODE_READ) {
358                 if (!(inode->i_mode & S_IRUGO) || !ops->show)
359                         goto err_out;
360         }
361 
362         /* No error? Great, allocate a buffer for the file, and store it
363          * it in file->private_data for easy access.
364          */
365         error = -ENOMEM;
366         buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
367         if (!buffer)
368                 goto err_out;
369 
370         mutex_init(&buffer->mutex);
371         buffer->needs_read_fill = 1;
372         buffer->ops = ops;
373         file->private_data = buffer;
374 
375         /* make sure we have open dirent struct */
376         error = sysfs_get_open_dirent(attr_sd, buffer);
377         if (error)
378                 goto err_free;
379 
380         /* open succeeded, put active references */
381         sysfs_put_active_two(attr_sd);
382         return 0;
383 
384  err_free:
385         kfree(buffer);
386  err_out:
387         sysfs_put_active_two(attr_sd);
388         return error;
389 }
390 
391 static int sysfs_release(struct inode *inode, struct file *filp)
392 {
393         struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
394         struct sysfs_buffer *buffer = filp->private_data;
395 
396         sysfs_put_open_dirent(sd, buffer);
397 
398         if (buffer->page)
399                 free_page((unsigned long)buffer->page);
400         kfree(buffer);
401 
402         return 0;
403 }
404 
405 /* Sysfs attribute files are pollable.  The idea is that you read
406  * the content and then you use 'poll' or 'select' to wait for
407  * the content to change.  When the content changes (assuming the
408  * manager for the kobject supports notification), poll will
409  * return POLLERR|POLLPRI, and select will return the fd whether
410  * it is waiting for read, write, or exceptions.
411  * Once poll/select indicates that the value has changed, you
412  * need to close and re-open the file, as simply seeking and reading
413  * again will not get new data, or reset the state of 'poll'.
414  * Reminder: this only works for attributes which actively support
415  * it, and it is not possible to test an attribute from userspace
416  * to see if it supports poll (Neither 'poll' nor 'select' return
417  * an appropriate error code).  When in doubt, set a suitable timeout value.
418  */
419 static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
420 {
421         struct sysfs_buffer * buffer = filp->private_data;
422         struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
423         struct sysfs_open_dirent *od = attr_sd->s_attr.open;
424 
425         /* need parent for the kobj, grab both */
426         if (!sysfs_get_active_two(attr_sd))
427                 goto trigger;
428 
429         poll_wait(filp, &od->poll, wait);
430 
431         sysfs_put_active_two(attr_sd);
432 
433         if (buffer->event != atomic_read(&od->event))
434                 goto trigger;
435 
436         return 0;
437 
438  trigger:
439         buffer->needs_read_fill = 1;
440         return POLLERR|POLLPRI;
441 }
442 
443 void sysfs_notify(struct kobject *k, char *dir, char *attr)
444 {
445         struct sysfs_dirent *sd = k->sd;
446 
447         mutex_lock(&sysfs_mutex);
448 
449         if (sd && dir)
450                 sd = sysfs_find_dirent(sd, dir);
451         if (sd && attr)
452                 sd = sysfs_find_dirent(sd, attr);
453         if (sd) {
454                 struct sysfs_open_dirent *od;
455 
456                 spin_lock(&sysfs_open_dirent_lock);
457 
458                 od = sd->s_attr.open;
459                 if (od) {
460                         atomic_inc(&od->event);
461                         wake_up_interruptible(&od->poll);
462                 }
463 
464                 spin_unlock(&sysfs_open_dirent_lock);
465         }
466 
467         mutex_unlock(&sysfs_mutex);
468 }
469 EXPORT_SYMBOL_GPL(sysfs_notify);
470 
471 const struct file_operations sysfs_file_operations = {
472         .read           = sysfs_read_file,
473         .write          = sysfs_write_file,
474         .llseek         = generic_file_llseek,
475         .open           = sysfs_open_file,
476         .release        = sysfs_release,
477         .poll           = sysfs_poll,
478 };
479 
480 
481 int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
482                    int type)
483 {
484         umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
485         struct sysfs_addrm_cxt acxt;
486         struct sysfs_dirent *sd;
487         int rc;
488 
489         sd = sysfs_new_dirent(attr->name, mode, type);
490         if (!sd)
491                 return -ENOMEM;
492         sd->s_attr.attr = (void *)attr;
493 
494         sysfs_addrm_start(&acxt, dir_sd);
495         rc = sysfs_add_one(&acxt, sd);
496         sysfs_addrm_finish(&acxt);
497 
498         if (rc)
499                 sysfs_put(sd);
500 
501         return rc;
502 }
503 
504 
505 /**
506  *      sysfs_create_file - create an attribute file for an object.
507  *      @kobj:  object we're creating for. 
508  *      @attr:  attribute descriptor.
509  */
510 
511 int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
512 {
513         BUG_ON(!kobj || !kobj->sd || !attr);
514 
515         return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
516 
517 }
518 
519 
520 /**
521  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
522  * @kobj: object we're acting for.
523  * @attr: attribute descriptor.
524  * @group: group name.
525  */
526 int sysfs_add_file_to_group(struct kobject *kobj,
527                 const struct attribute *attr, const char *group)
528 {
529         struct sysfs_dirent *dir_sd;
530         int error;
531 
532         if (group)
533                 dir_sd = sysfs_get_dirent(kobj->sd, group);
534         else
535                 dir_sd = sysfs_get(kobj->sd);
536 
537         if (!dir_sd)
538                 return -ENOENT;
539 
540         error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
541         sysfs_put(dir_sd);
542 
543         return error;
544 }
545 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
546 
547 /**
548  * sysfs_chmod_file - update the modified mode value on an object attribute.
549  * @kobj: object we're acting for.
550  * @attr: attribute descriptor.
551  * @mode: file permissions.
552  *
553  */
554 int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
555 {
556         struct sysfs_dirent *victim_sd = NULL;
557         struct dentry *victim = NULL;
558         struct inode * inode;
559         struct iattr newattrs;
560         int rc;
561 
562         rc = -ENOENT;
563         victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
564         if (!victim_sd)
565                 goto out;
566 
567         mutex_lock(&sysfs_rename_mutex);
568         victim = sysfs_get_dentry(victim_sd);
569         mutex_unlock(&sysfs_rename_mutex);
570         if (IS_ERR(victim)) {
571                 rc = PTR_ERR(victim);
572                 victim = NULL;
573                 goto out;
574         }
575 
576         inode = victim->d_inode;
577 
578         mutex_lock(&inode->i_mutex);
579 
580         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
581         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
582         rc = notify_change(victim, &newattrs);
583 
584         if (rc == 0) {
585                 mutex_lock(&sysfs_mutex);
586                 victim_sd->s_mode = newattrs.ia_mode;
587                 mutex_unlock(&sysfs_mutex);
588         }
589 
590         mutex_unlock(&inode->i_mutex);
591  out:
592         dput(victim);
593         sysfs_put(victim_sd);
594         return rc;
595 }
596 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
597 
598 
599 /**
600  *      sysfs_remove_file - remove an object attribute.
601  *      @kobj:  object we're acting for.
602  *      @attr:  attribute descriptor.
603  *
604  *      Hash the attribute name and kill the victim.
605  */
606 
607 void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
608 {
609         sysfs_hash_and_remove(kobj->sd, attr->name);
610 }
611 
612 
613 /**
614  * sysfs_remove_file_from_group - remove an attribute file from a group.
615  * @kobj: object we're acting for.
616  * @attr: attribute descriptor.
617  * @group: group name.
618  */
619 void sysfs_remove_file_from_group(struct kobject *kobj,
620                 const struct attribute *attr, const char *group)
621 {
622         struct sysfs_dirent *dir_sd;
623 
624         if (group)
625                 dir_sd = sysfs_get_dirent(kobj->sd, group);
626         else
627                 dir_sd = sysfs_get(kobj->sd);
628         if (dir_sd) {
629                 sysfs_hash_and_remove(dir_sd, attr->name);
630                 sysfs_put(dir_sd);
631         }
632 }
633 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
634 
635 struct sysfs_schedule_callback_struct {
636         struct kobject          *kobj;
637         void                    (*func)(void *);
638         void                    *data;
639         struct module           *owner;
640         struct work_struct      work;
641 };
642 
643 static void sysfs_schedule_callback_work(struct work_struct *work)
644 {
645         struct sysfs_schedule_callback_struct *ss = container_of(work,
646                         struct sysfs_schedule_callback_struct, work);
647 
648         (ss->func)(ss->data);
649         kobject_put(ss->kobj);
650         module_put(ss->owner);
651         kfree(ss);
652 }
653 
654 /**
655  * sysfs_schedule_callback - helper to schedule a callback for a kobject
656  * @kobj: object we're acting for.
657  * @func: callback function to invoke later.
658  * @data: argument to pass to @func.
659  * @owner: module owning the callback code
660  *
661  * sysfs attribute methods must not unregister themselves or their parent
662  * kobject (which would amount to the same thing).  Attempts to do so will
663  * deadlock, since unregistration is mutually exclusive with driver
664  * callbacks.
665  *
666  * Instead methods can call this routine, which will attempt to allocate
667  * and schedule a workqueue request to call back @func with @data as its
668  * argument in the workqueue's process context.  @kobj will be pinned
669  * until @func returns.
670  *
671  * Returns 0 if the request was submitted, -ENOMEM if storage could not
672  * be allocated, -ENODEV if a reference to @owner isn't available.
673  */
674 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
675                 void *data, struct module *owner)
676 {
677         struct sysfs_schedule_callback_struct *ss;
678 
679         if (!try_module_get(owner))
680                 return -ENODEV;
681         ss = kmalloc(sizeof(*ss), GFP_KERNEL);
682         if (!ss) {
683                 module_put(owner);
684                 return -ENOMEM;
685         }
686         kobject_get(kobj);
687         ss->kobj = kobj;
688         ss->func = func;
689         ss->data = data;
690         ss->owner = owner;
691         INIT_WORK(&ss->work, sysfs_schedule_callback_work);
692         schedule_work(&ss->work);
693         return 0;
694 }
695 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
696 
697 
698 EXPORT_SYMBOL_GPL(sysfs_create_file);
699 EXPORT_SYMBOL_GPL(sysfs_remove_file);
700 
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