blob: 146f1dedec844ced95a9055e31e701365b4b241e [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * file.c - operations for regular (text) files.
3 */
4
5#include <linux/module.h>
Robert Love0eeca282005-07-12 17:06:03 -04006#include <linux/fsnotify.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07007#include <linux/kobject.h>
Christoph Hellwig5f45f1a2005-06-23 00:09:12 -07008#include <linux/namei.h>
NeilBrown4508a7a2006-03-20 17:53:53 +11009#include <linux/poll.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070010#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
Martin Waitz3d410882005-06-23 22:05:21 -070018/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070019 * Subsystem file operations.
20 * These operations allow subsystems to have files that can be
21 * read/written.
22 */
23static ssize_t
24subsys_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);
Dmitry Torokhovc76d0ab2005-04-29 01:22:00 -050028 ssize_t ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -070029
30 if (sattr->show)
31 ret = sattr->show(s,page);
32 return ret;
33}
34
35static ssize_t
36subsys_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);
Dmitry Torokhovc76d0ab2005-04-29 01:22:00 -050041 ssize_t ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -070042
43 if (sattr->store)
44 ret = sattr->store(s,page,count);
45 return ret;
46}
47
48static struct sysfs_ops subsys_sysfs_ops = {
49 .show = subsys_attr_show,
50 .store = subsys_attr_store,
51};
52
53
54struct 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;
NeilBrown4508a7a2006-03-20 17:53:53 +110061 int event;
Linus Torvalds1da177e2005-04-16 15:20:36 -070062};
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 */
75static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
76{
NeilBrown4508a7a2006-03-20 17:53:53 +110077 struct sysfs_dirent * sd = dentry->d_fsdata;
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 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
NeilBrown4508a7a2006-03-20 17:53:53 +110089 buffer->event = atomic_read(&sd->s_event);
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 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.
Martin Waitz67be2dd2005-05-01 08:59:26 -0700104 * @buf: user-passed buffer.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 * @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 */
113static 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
149static ssize_t
150sysfs_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 }
Zach Brown5c1fdf42006-10-03 01:16:06 -0700160 pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
161 __FUNCTION__, count, *ppos, buffer->page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162 retval = flush_read_buffer(buffer,buf,count,ppos);
163out:
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.
Martin Waitz67be2dd2005-05-01 08:59:26 -0700172 * @buf: data from user.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 * @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
179static int
180fill_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)
Greg Kroah-Hartman6e0dd742006-03-31 15:37:06 -0800190 count = PAGE_SIZE - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 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.
Martin Waitz3d410882005-06-23 22:05:21 -0700199 * @dentry: dentry to the attribute
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200 * @buffer: data buffer for file.
Martin Waitz3d410882005-06-23 22:05:21 -0700201 * @count: number of bytes
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202 *
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
208static int
209flush_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
236static ssize_t
237sysfs_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
252static 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 */
Eric Sesterhenn58d49282006-02-22 11:18:15 +0100308 buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309 if (buffer) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 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
330static int sysfs_open_file(struct inode * inode, struct file * filp)
331{
332 return check_perm(inode,filp);
333}
334
335static 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
NeilBrown4508a7a2006-03-20 17:53:53 +1100355/* 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 */
369static 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
387static 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
407void 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}
424EXPORT_SYMBOL_GPL(sysfs_notify);
425
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -0800426const struct file_operations sysfs_file_operations = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427 .read = sysfs_read_file,
428 .write = sysfs_write_file,
429 .llseek = generic_file_llseek,
430 .open = sysfs_open_file,
431 .release = sysfs_release,
NeilBrown4508a7a2006-03-20 17:53:53 +1100432 .poll = sysfs_poll,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433};
434
435
436int 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;
Maneesh Sonic5168652006-03-09 19:40:14 +0530440 int error = -EEXIST;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800442 mutex_lock(&dir->d_inode->i_mutex);
Maneesh Sonic5168652006-03-09 19:40:14 +0530443 if (!sysfs_dirent_exist(parent_sd, attr->name))
444 error = sysfs_make_dirent(parent_sd, NULL, (void *)attr,
445 mode, type);
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800446 mutex_unlock(&dir->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447
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
458int 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.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471 */
472int 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
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800478 mutex_lock(&dir->d_inode->i_mutex);
Christoph Hellwig5f45f1a2005-06-23 00:09:12 -0700479 victim = lookup_one_len(attr->name, dir, strlen(attr->name));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 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;
Robert Love0eeca282005-07-12 17:06:03 -0400485 fsnotify_modify(victim);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700486
487 /**
488 * Drop reference from initial sysfs_get_dentry().
489 */
490 dput(victim);
491 res = 0;
492 } else
493 d_drop(victim);
494
495 /**
496 * Drop the reference acquired from sysfs_get_dentry() above.
497 */
498 dput(victim);
499 }
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800500 mutex_unlock(&dir->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501
502 return res;
503}
504
505
506/**
Kay Sievers31e5abe2005-04-18 21:57:32 -0700507 * sysfs_chmod_file - update the modified mode value on an object attribute.
508 * @kobj: object we're acting for.
509 * @attr: attribute descriptor.
510 * @mode: file permissions.
511 *
512 */
513int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
514{
515 struct dentry *dir = kobj->dentry;
516 struct dentry *victim;
Maneesh Sonibc062b12005-07-29 12:13:35 -0700517 struct inode * inode;
518 struct iattr newattrs;
Kay Sievers31e5abe2005-04-18 21:57:32 -0700519 int res = -ENOENT;
520
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800521 mutex_lock(&dir->d_inode->i_mutex);
Christoph Hellwig5f45f1a2005-06-23 00:09:12 -0700522 victim = lookup_one_len(attr->name, dir, strlen(attr->name));
Kay Sievers31e5abe2005-04-18 21:57:32 -0700523 if (!IS_ERR(victim)) {
524 if (victim->d_inode &&
525 (victim->d_parent->d_inode == dir->d_inode)) {
Maneesh Sonibc062b12005-07-29 12:13:35 -0700526 inode = victim->d_inode;
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800527 mutex_lock(&inode->i_mutex);
Maneesh Sonibc062b12005-07-29 12:13:35 -0700528 newattrs.ia_mode = (mode & S_IALLUGO) |
529 (inode->i_mode & ~S_IALLUGO);
530 newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
531 res = notify_change(victim, &newattrs);
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800532 mutex_unlock(&inode->i_mutex);
Kay Sievers31e5abe2005-04-18 21:57:32 -0700533 }
Maneesh Sonibc062b12005-07-29 12:13:35 -0700534 dput(victim);
Kay Sievers31e5abe2005-04-18 21:57:32 -0700535 }
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800536 mutex_unlock(&dir->d_inode->i_mutex);
Kay Sievers31e5abe2005-04-18 21:57:32 -0700537
538 return res;
539}
540EXPORT_SYMBOL_GPL(sysfs_chmod_file);
541
542
543/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544 * sysfs_remove_file - remove an object attribute.
545 * @kobj: object we're acting for.
546 * @attr: attribute descriptor.
547 *
548 * Hash the attribute name and kill the victim.
549 */
550
551void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
552{
553 sysfs_hash_and_remove(kobj->dentry,attr->name);
554}
555
556
557EXPORT_SYMBOL_GPL(sysfs_create_file);
558EXPORT_SYMBOL_GPL(sysfs_remove_file);
559EXPORT_SYMBOL_GPL(sysfs_update_file);