Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * file.c - operations for regular (text) files. | |
3 | */ | |
4 | ||
5 | #include <linux/module.h> | |
0eeca283 | 6 | #include <linux/fsnotify.h> |
1da177e4 | 7 | #include <linux/kobject.h> |
5f45f1a7 | 8 | #include <linux/namei.h> |
4508a7a7 | 9 | #include <linux/poll.h> |
1da177e4 LT |
10 | #include <asm/uaccess.h> |
11 | #include <asm/semaphore.h> | |
12 | ||
13 | #include "sysfs.h" | |
14 | ||
15 | #define to_subsys(k) container_of(k,struct subsystem,kset.kobj) | |
16 | #define to_sattr(a) container_of(a,struct subsys_attribute,attr) | |
17 | ||
3d41088f | 18 | /* |
1da177e4 LT |
19 | * Subsystem file operations. |
20 | * These operations allow subsystems to have files that can be | |
21 | * read/written. | |
22 | */ | |
23 | static ssize_t | |
24 | subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page) | |
25 | { | |
26 | struct subsystem * s = to_subsys(kobj); | |
27 | struct subsys_attribute * sattr = to_sattr(attr); | |
c76d0abd | 28 | ssize_t ret = -EIO; |
1da177e4 LT |
29 | |
30 | if (sattr->show) | |
31 | ret = sattr->show(s,page); | |
32 | return ret; | |
33 | } | |
34 | ||
35 | static ssize_t | |
36 | subsys_attr_store(struct kobject * kobj, struct attribute * attr, | |
37 | const char * page, size_t count) | |
38 | { | |
39 | struct subsystem * s = to_subsys(kobj); | |
40 | struct subsys_attribute * sattr = to_sattr(attr); | |
c76d0abd | 41 | ssize_t ret = -EIO; |
1da177e4 LT |
42 | |
43 | if (sattr->store) | |
44 | ret = sattr->store(s,page,count); | |
45 | return ret; | |
46 | } | |
47 | ||
48 | static struct sysfs_ops subsys_sysfs_ops = { | |
49 | .show = subsys_attr_show, | |
50 | .store = subsys_attr_store, | |
51 | }; | |
52 | ||
53 | ||
54 | struct sysfs_buffer { | |
55 | size_t count; | |
56 | loff_t pos; | |
57 | char * page; | |
58 | struct sysfs_ops * ops; | |
59 | struct semaphore sem; | |
60 | int needs_read_fill; | |
4508a7a7 | 61 | int event; |
1da177e4 LT |
62 | }; |
63 | ||
64 | ||
65 | /** | |
66 | * fill_read_buffer - allocate and fill buffer from object. | |
67 | * @dentry: dentry pointer. | |
68 | * @buffer: data buffer for file. | |
69 | * | |
70 | * Allocate @buffer->page, if it hasn't been already, then call the | |
71 | * kobject's show() method to fill the buffer with this attribute's | |
72 | * data. | |
73 | * This is called only once, on the file's first read. | |
74 | */ | |
75 | static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer) | |
76 | { | |
4508a7a7 | 77 | struct sysfs_dirent * sd = dentry->d_fsdata; |
1da177e4 LT |
78 | struct attribute * attr = to_attr(dentry); |
79 | struct kobject * kobj = to_kobj(dentry->d_parent); | |
80 | struct sysfs_ops * ops = buffer->ops; | |
81 | int ret = 0; | |
82 | ssize_t count; | |
83 | ||
84 | if (!buffer->page) | |
85 | buffer->page = (char *) get_zeroed_page(GFP_KERNEL); | |
86 | if (!buffer->page) | |
87 | return -ENOMEM; | |
88 | ||
4508a7a7 | 89 | buffer->event = atomic_read(&sd->s_event); |
1da177e4 LT |
90 | count = ops->show(kobj,attr,buffer->page); |
91 | buffer->needs_read_fill = 0; | |
92 | BUG_ON(count > (ssize_t)PAGE_SIZE); | |
93 | if (count >= 0) | |
94 | buffer->count = count; | |
95 | else | |
96 | ret = count; | |
97 | return ret; | |
98 | } | |
99 | ||
100 | ||
101 | /** | |
102 | * flush_read_buffer - push buffer to userspace. | |
103 | * @buffer: data buffer for file. | |
67be2dd1 | 104 | * @buf: user-passed buffer. |
1da177e4 LT |
105 | * @count: number of bytes requested. |
106 | * @ppos: file position. | |
107 | * | |
108 | * Copy the buffer we filled in fill_read_buffer() to userspace. | |
109 | * This is done at the reader's leisure, copying and advancing | |
110 | * the amount they specify each time. | |
111 | * This may be called continuously until the buffer is empty. | |
112 | */ | |
113 | static int flush_read_buffer(struct sysfs_buffer * buffer, char __user * buf, | |
114 | size_t count, loff_t * ppos) | |
115 | { | |
116 | int error; | |
117 | ||
118 | if (*ppos > buffer->count) | |
119 | return 0; | |
120 | ||
121 | if (count > (buffer->count - *ppos)) | |
122 | count = buffer->count - *ppos; | |
123 | ||
124 | error = copy_to_user(buf,buffer->page + *ppos,count); | |
125 | if (!error) | |
126 | *ppos += count; | |
127 | return error ? -EFAULT : count; | |
128 | } | |
129 | ||
130 | /** | |
131 | * sysfs_read_file - read an attribute. | |
132 | * @file: file pointer. | |
133 | * @buf: buffer to fill. | |
134 | * @count: number of bytes to read. | |
135 | * @ppos: starting offset in file. | |
136 | * | |
137 | * Userspace wants to read an attribute file. The attribute descriptor | |
138 | * is in the file's ->d_fsdata. The target object is in the directory's | |
139 | * ->d_fsdata. | |
140 | * | |
141 | * We call fill_read_buffer() to allocate and fill the buffer from the | |
142 | * object's show() method exactly once (if the read is happening from | |
143 | * the beginning of the file). That should fill the entire buffer with | |
144 | * all the data the object has to offer for that attribute. | |
145 | * We then call flush_read_buffer() to copy the buffer to userspace | |
146 | * in the increments specified. | |
147 | */ | |
148 | ||
149 | static ssize_t | |
150 | sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) | |
151 | { | |
152 | struct sysfs_buffer * buffer = file->private_data; | |
153 | ssize_t retval = 0; | |
154 | ||
155 | down(&buffer->sem); | |
156 | if (buffer->needs_read_fill) { | |
157 | if ((retval = fill_read_buffer(file->f_dentry,buffer))) | |
158 | goto out; | |
159 | } | |
5c1fdf41 ZB |
160 | pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n", |
161 | __FUNCTION__, count, *ppos, buffer->page); | |
1da177e4 LT |
162 | retval = flush_read_buffer(buffer,buf,count,ppos); |
163 | out: | |
164 | up(&buffer->sem); | |
165 | return retval; | |
166 | } | |
167 | ||
168 | ||
169 | /** | |
170 | * fill_write_buffer - copy buffer from userspace. | |
171 | * @buffer: data buffer for file. | |
67be2dd1 | 172 | * @buf: data from user. |
1da177e4 LT |
173 | * @count: number of bytes in @userbuf. |
174 | * | |
175 | * Allocate @buffer->page if it hasn't been already, then | |
176 | * copy the user-supplied buffer into it. | |
177 | */ | |
178 | ||
179 | static int | |
180 | fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count) | |
181 | { | |
182 | int error; | |
183 | ||
184 | if (!buffer->page) | |
185 | buffer->page = (char *)get_zeroed_page(GFP_KERNEL); | |
186 | if (!buffer->page) | |
187 | return -ENOMEM; | |
188 | ||
189 | if (count >= PAGE_SIZE) | |
6e0dd741 | 190 | count = PAGE_SIZE - 1; |
1da177e4 LT |
191 | error = copy_from_user(buffer->page,buf,count); |
192 | buffer->needs_read_fill = 1; | |
193 | return error ? -EFAULT : count; | |
194 | } | |
195 | ||
196 | ||
197 | /** | |
198 | * flush_write_buffer - push buffer to kobject. | |
3d41088f | 199 | * @dentry: dentry to the attribute |
1da177e4 | 200 | * @buffer: data buffer for file. |
3d41088f | 201 | * @count: number of bytes |
1da177e4 LT |
202 | * |
203 | * Get the correct pointers for the kobject and the attribute we're | |
204 | * dealing with, then call the store() method for the attribute, | |
205 | * passing the buffer that we acquired in fill_write_buffer(). | |
206 | */ | |
207 | ||
208 | static int | |
209 | flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count) | |
210 | { | |
211 | struct attribute * attr = to_attr(dentry); | |
212 | struct kobject * kobj = to_kobj(dentry->d_parent); | |
213 | struct sysfs_ops * ops = buffer->ops; | |
214 | ||
215 | return ops->store(kobj,attr,buffer->page,count); | |
216 | } | |
217 | ||
218 | ||
219 | /** | |
220 | * sysfs_write_file - write an attribute. | |
221 | * @file: file pointer | |
222 | * @buf: data to write | |
223 | * @count: number of bytes | |
224 | * @ppos: starting offset | |
225 | * | |
226 | * Similar to sysfs_read_file(), though working in the opposite direction. | |
227 | * We allocate and fill the data from the user in fill_write_buffer(), | |
228 | * then push it to the kobject in flush_write_buffer(). | |
229 | * There is no easy way for us to know if userspace is only doing a partial | |
230 | * write, so we don't support them. We expect the entire buffer to come | |
231 | * on the first write. | |
232 | * Hint: if you're writing a value, first read the file, modify only the | |
233 | * the value you're changing, then write entire buffer back. | |
234 | */ | |
235 | ||
236 | static ssize_t | |
237 | sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) | |
238 | { | |
239 | struct sysfs_buffer * buffer = file->private_data; | |
240 | ssize_t len; | |
241 | ||
242 | down(&buffer->sem); | |
243 | len = fill_write_buffer(buffer, buf, count); | |
244 | if (len > 0) | |
245 | len = flush_write_buffer(file->f_dentry, buffer, len); | |
246 | if (len > 0) | |
247 | *ppos += len; | |
248 | up(&buffer->sem); | |
249 | return len; | |
250 | } | |
251 | ||
252 | static int check_perm(struct inode * inode, struct file * file) | |
253 | { | |
254 | struct kobject *kobj = sysfs_get_kobject(file->f_dentry->d_parent); | |
255 | struct attribute * attr = to_attr(file->f_dentry); | |
256 | struct sysfs_buffer * buffer; | |
257 | struct sysfs_ops * ops = NULL; | |
258 | int error = 0; | |
259 | ||
260 | if (!kobj || !attr) | |
261 | goto Einval; | |
262 | ||
263 | /* Grab the module reference for this attribute if we have one */ | |
264 | if (!try_module_get(attr->owner)) { | |
265 | error = -ENODEV; | |
266 | goto Done; | |
267 | } | |
268 | ||
269 | /* if the kobject has no ktype, then we assume that it is a subsystem | |
270 | * itself, and use ops for it. | |
271 | */ | |
272 | if (kobj->kset && kobj->kset->ktype) | |
273 | ops = kobj->kset->ktype->sysfs_ops; | |
274 | else if (kobj->ktype) | |
275 | ops = kobj->ktype->sysfs_ops; | |
276 | else | |
277 | ops = &subsys_sysfs_ops; | |
278 | ||
279 | /* No sysfs operations, either from having no subsystem, | |
280 | * or the subsystem have no operations. | |
281 | */ | |
282 | if (!ops) | |
283 | goto Eaccess; | |
284 | ||
285 | /* File needs write support. | |
286 | * The inode's perms must say it's ok, | |
287 | * and we must have a store method. | |
288 | */ | |
289 | if (file->f_mode & FMODE_WRITE) { | |
290 | ||
291 | if (!(inode->i_mode & S_IWUGO) || !ops->store) | |
292 | goto Eaccess; | |
293 | ||
294 | } | |
295 | ||
296 | /* File needs read support. | |
297 | * The inode's perms must say it's ok, and we there | |
298 | * must be a show method for it. | |
299 | */ | |
300 | if (file->f_mode & FMODE_READ) { | |
301 | if (!(inode->i_mode & S_IRUGO) || !ops->show) | |
302 | goto Eaccess; | |
303 | } | |
304 | ||
305 | /* No error? Great, allocate a buffer for the file, and store it | |
306 | * it in file->private_data for easy access. | |
307 | */ | |
58d49283 | 308 | buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL); |
1da177e4 | 309 | if (buffer) { |
1da177e4 LT |
310 | init_MUTEX(&buffer->sem); |
311 | buffer->needs_read_fill = 1; | |
312 | buffer->ops = ops; | |
313 | file->private_data = buffer; | |
314 | } else | |
315 | error = -ENOMEM; | |
316 | goto Done; | |
317 | ||
318 | Einval: | |
319 | error = -EINVAL; | |
320 | goto Done; | |
321 | Eaccess: | |
322 | error = -EACCES; | |
323 | module_put(attr->owner); | |
324 | Done: | |
325 | if (error && kobj) | |
326 | kobject_put(kobj); | |
327 | return error; | |
328 | } | |
329 | ||
330 | static int sysfs_open_file(struct inode * inode, struct file * filp) | |
331 | { | |
332 | return check_perm(inode,filp); | |
333 | } | |
334 | ||
335 | static int sysfs_release(struct inode * inode, struct file * filp) | |
336 | { | |
337 | struct kobject * kobj = to_kobj(filp->f_dentry->d_parent); | |
338 | struct attribute * attr = to_attr(filp->f_dentry); | |
339 | struct module * owner = attr->owner; | |
340 | struct sysfs_buffer * buffer = filp->private_data; | |
341 | ||
342 | if (kobj) | |
343 | kobject_put(kobj); | |
344 | /* After this point, attr should not be accessed. */ | |
345 | module_put(owner); | |
346 | ||
347 | if (buffer) { | |
348 | if (buffer->page) | |
349 | free_page((unsigned long)buffer->page); | |
350 | kfree(buffer); | |
351 | } | |
352 | return 0; | |
353 | } | |
354 | ||
4508a7a7 N |
355 | /* Sysfs attribute files are pollable. The idea is that you read |
356 | * the content and then you use 'poll' or 'select' to wait for | |
357 | * the content to change. When the content changes (assuming the | |
358 | * manager for the kobject supports notification), poll will | |
359 | * return POLLERR|POLLPRI, and select will return the fd whether | |
360 | * it is waiting for read, write, or exceptions. | |
361 | * Once poll/select indicates that the value has changed, you | |
362 | * need to close and re-open the file, as simply seeking and reading | |
363 | * again will not get new data, or reset the state of 'poll'. | |
364 | * Reminder: this only works for attributes which actively support | |
365 | * it, and it is not possible to test an attribute from userspace | |
366 | * to see if it supports poll (Nether 'poll' or 'select' return | |
367 | * an appropriate error code). When in doubt, set a suitable timeout value. | |
368 | */ | |
369 | static unsigned int sysfs_poll(struct file *filp, poll_table *wait) | |
370 | { | |
371 | struct sysfs_buffer * buffer = filp->private_data; | |
372 | struct kobject * kobj = to_kobj(filp->f_dentry->d_parent); | |
373 | struct sysfs_dirent * sd = filp->f_dentry->d_fsdata; | |
374 | int res = 0; | |
375 | ||
376 | poll_wait(filp, &kobj->poll, wait); | |
377 | ||
378 | if (buffer->event != atomic_read(&sd->s_event)) { | |
379 | res = POLLERR|POLLPRI; | |
380 | buffer->needs_read_fill = 1; | |
381 | } | |
382 | ||
383 | return res; | |
384 | } | |
385 | ||
386 | ||
387 | static struct dentry *step_down(struct dentry *dir, const char * name) | |
388 | { | |
389 | struct dentry * de; | |
390 | ||
391 | if (dir == NULL || dir->d_inode == NULL) | |
392 | return NULL; | |
393 | ||
394 | mutex_lock(&dir->d_inode->i_mutex); | |
395 | de = lookup_one_len(name, dir, strlen(name)); | |
396 | mutex_unlock(&dir->d_inode->i_mutex); | |
397 | dput(dir); | |
398 | if (IS_ERR(de)) | |
399 | return NULL; | |
400 | if (de->d_inode == NULL) { | |
401 | dput(de); | |
402 | return NULL; | |
403 | } | |
404 | return de; | |
405 | } | |
406 | ||
407 | void sysfs_notify(struct kobject * k, char *dir, char *attr) | |
408 | { | |
409 | struct dentry *de = k->dentry; | |
410 | if (de) | |
411 | dget(de); | |
412 | if (de && dir) | |
413 | de = step_down(de, dir); | |
414 | if (de && attr) | |
415 | de = step_down(de, attr); | |
416 | if (de) { | |
417 | struct sysfs_dirent * sd = de->d_fsdata; | |
418 | if (sd) | |
419 | atomic_inc(&sd->s_event); | |
420 | wake_up_interruptible(&k->poll); | |
421 | dput(de); | |
422 | } | |
423 | } | |
424 | EXPORT_SYMBOL_GPL(sysfs_notify); | |
425 | ||
4b6f5d20 | 426 | const struct file_operations sysfs_file_operations = { |
1da177e4 LT |
427 | .read = sysfs_read_file, |
428 | .write = sysfs_write_file, | |
429 | .llseek = generic_file_llseek, | |
430 | .open = sysfs_open_file, | |
431 | .release = sysfs_release, | |
4508a7a7 | 432 | .poll = sysfs_poll, |
1da177e4 LT |
433 | }; |
434 | ||
435 | ||
436 | int sysfs_add_file(struct dentry * dir, const struct attribute * attr, int type) | |
437 | { | |
438 | struct sysfs_dirent * parent_sd = dir->d_fsdata; | |
439 | umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG; | |
c516865c | 440 | int error = -EEXIST; |
1da177e4 | 441 | |
1b1dcc1b | 442 | mutex_lock(&dir->d_inode->i_mutex); |
c516865c MS |
443 | if (!sysfs_dirent_exist(parent_sd, attr->name)) |
444 | error = sysfs_make_dirent(parent_sd, NULL, (void *)attr, | |
445 | mode, type); | |
1b1dcc1b | 446 | mutex_unlock(&dir->d_inode->i_mutex); |
1da177e4 LT |
447 | |
448 | return error; | |
449 | } | |
450 | ||
451 | ||
452 | /** | |
453 | * sysfs_create_file - create an attribute file for an object. | |
454 | * @kobj: object we're creating for. | |
455 | * @attr: atrribute descriptor. | |
456 | */ | |
457 | ||
458 | int sysfs_create_file(struct kobject * kobj, const struct attribute * attr) | |
459 | { | |
460 | BUG_ON(!kobj || !kobj->dentry || !attr); | |
461 | ||
462 | return sysfs_add_file(kobj->dentry, attr, SYSFS_KOBJ_ATTR); | |
463 | ||
464 | } | |
465 | ||
466 | ||
467 | /** | |
468 | * sysfs_update_file - update the modified timestamp on an object attribute. | |
469 | * @kobj: object we're acting for. | |
470 | * @attr: attribute descriptor. | |
1da177e4 LT |
471 | */ |
472 | int sysfs_update_file(struct kobject * kobj, const struct attribute * attr) | |
473 | { | |
474 | struct dentry * dir = kobj->dentry; | |
475 | struct dentry * victim; | |
476 | int res = -ENOENT; | |
477 | ||
1b1dcc1b | 478 | mutex_lock(&dir->d_inode->i_mutex); |
5f45f1a7 | 479 | victim = lookup_one_len(attr->name, dir, strlen(attr->name)); |
1da177e4 LT |
480 | if (!IS_ERR(victim)) { |
481 | /* make sure dentry is really there */ | |
482 | if (victim->d_inode && | |
483 | (victim->d_parent->d_inode == dir->d_inode)) { | |
484 | victim->d_inode->i_mtime = CURRENT_TIME; | |
0eeca283 | 485 | fsnotify_modify(victim); |
1da177e4 LT |
486 | res = 0; |
487 | } else | |
488 | d_drop(victim); | |
489 | ||
490 | /** | |
97a50184 | 491 | * Drop the reference acquired from lookup_one_len() above. |
1da177e4 LT |
492 | */ |
493 | dput(victim); | |
494 | } | |
1b1dcc1b | 495 | mutex_unlock(&dir->d_inode->i_mutex); |
1da177e4 LT |
496 | |
497 | return res; | |
498 | } | |
499 | ||
500 | ||
31e5abe9 KS |
501 | /** |
502 | * sysfs_chmod_file - update the modified mode value on an object attribute. | |
503 | * @kobj: object we're acting for. | |
504 | * @attr: attribute descriptor. | |
505 | * @mode: file permissions. | |
506 | * | |
507 | */ | |
508 | int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode) | |
509 | { | |
510 | struct dentry *dir = kobj->dentry; | |
511 | struct dentry *victim; | |
bc062b1b MS |
512 | struct inode * inode; |
513 | struct iattr newattrs; | |
31e5abe9 KS |
514 | int res = -ENOENT; |
515 | ||
1b1dcc1b | 516 | mutex_lock(&dir->d_inode->i_mutex); |
5f45f1a7 | 517 | victim = lookup_one_len(attr->name, dir, strlen(attr->name)); |
31e5abe9 KS |
518 | if (!IS_ERR(victim)) { |
519 | if (victim->d_inode && | |
520 | (victim->d_parent->d_inode == dir->d_inode)) { | |
bc062b1b | 521 | inode = victim->d_inode; |
1b1dcc1b | 522 | mutex_lock(&inode->i_mutex); |
bc062b1b MS |
523 | newattrs.ia_mode = (mode & S_IALLUGO) | |
524 | (inode->i_mode & ~S_IALLUGO); | |
525 | newattrs.ia_valid = ATTR_MODE | ATTR_CTIME; | |
526 | res = notify_change(victim, &newattrs); | |
1b1dcc1b | 527 | mutex_unlock(&inode->i_mutex); |
31e5abe9 | 528 | } |
bc062b1b | 529 | dput(victim); |
31e5abe9 | 530 | } |
1b1dcc1b | 531 | mutex_unlock(&dir->d_inode->i_mutex); |
31e5abe9 KS |
532 | |
533 | return res; | |
534 | } | |
535 | EXPORT_SYMBOL_GPL(sysfs_chmod_file); | |
536 | ||
537 | ||
1da177e4 LT |
538 | /** |
539 | * sysfs_remove_file - remove an object attribute. | |
540 | * @kobj: object we're acting for. | |
541 | * @attr: attribute descriptor. | |
542 | * | |
543 | * Hash the attribute name and kill the victim. | |
544 | */ | |
545 | ||
546 | void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr) | |
547 | { | |
548 | sysfs_hash_and_remove(kobj->dentry,attr->name); | |
549 | } | |
550 | ||
551 | ||
552 | EXPORT_SYMBOL_GPL(sysfs_create_file); | |
553 | EXPORT_SYMBOL_GPL(sysfs_remove_file); | |
554 | EXPORT_SYMBOL_GPL(sysfs_update_file); |