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1da177e4 LT |
1 | /* |
2 | * file.c - operations for regular (text) files. | |
3 | */ | |
4 | ||
5 | #include <linux/module.h> | |
6 | #include <linux/dnotify.h> | |
7 | #include <linux/kobject.h> | |
8 | #include <asm/uaccess.h> | |
9 | #include <asm/semaphore.h> | |
10 | ||
11 | #include "sysfs.h" | |
12 | ||
13 | #define to_subsys(k) container_of(k,struct subsystem,kset.kobj) | |
14 | #define to_sattr(a) container_of(a,struct subsys_attribute,attr) | |
15 | ||
16 | /** | |
17 | * Subsystem file operations. | |
18 | * These operations allow subsystems to have files that can be | |
19 | * read/written. | |
20 | */ | |
21 | static ssize_t | |
22 | subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page) | |
23 | { | |
24 | struct subsystem * s = to_subsys(kobj); | |
25 | struct subsys_attribute * sattr = to_sattr(attr); | |
26 | ssize_t ret = 0; | |
27 | ||
28 | if (sattr->show) | |
29 | ret = sattr->show(s,page); | |
30 | return ret; | |
31 | } | |
32 | ||
33 | static ssize_t | |
34 | subsys_attr_store(struct kobject * kobj, struct attribute * attr, | |
35 | const char * page, size_t count) | |
36 | { | |
37 | struct subsystem * s = to_subsys(kobj); | |
38 | struct subsys_attribute * sattr = to_sattr(attr); | |
39 | ssize_t ret = 0; | |
40 | ||
41 | if (sattr->store) | |
42 | ret = sattr->store(s,page,count); | |
43 | return ret; | |
44 | } | |
45 | ||
46 | static struct sysfs_ops subsys_sysfs_ops = { | |
47 | .show = subsys_attr_show, | |
48 | .store = subsys_attr_store, | |
49 | }; | |
50 | ||
51 | ||
52 | struct sysfs_buffer { | |
53 | size_t count; | |
54 | loff_t pos; | |
55 | char * page; | |
56 | struct sysfs_ops * ops; | |
57 | struct semaphore sem; | |
58 | int needs_read_fill; | |
59 | }; | |
60 | ||
61 | ||
62 | /** | |
63 | * fill_read_buffer - allocate and fill buffer from object. | |
64 | * @dentry: dentry pointer. | |
65 | * @buffer: data buffer for file. | |
66 | * | |
67 | * Allocate @buffer->page, if it hasn't been already, then call the | |
68 | * kobject's show() method to fill the buffer with this attribute's | |
69 | * data. | |
70 | * This is called only once, on the file's first read. | |
71 | */ | |
72 | static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer) | |
73 | { | |
74 | struct attribute * attr = to_attr(dentry); | |
75 | struct kobject * kobj = to_kobj(dentry->d_parent); | |
76 | struct sysfs_ops * ops = buffer->ops; | |
77 | int ret = 0; | |
78 | ssize_t count; | |
79 | ||
80 | if (!buffer->page) | |
81 | buffer->page = (char *) get_zeroed_page(GFP_KERNEL); | |
82 | if (!buffer->page) | |
83 | return -ENOMEM; | |
84 | ||
85 | count = ops->show(kobj,attr,buffer->page); | |
86 | buffer->needs_read_fill = 0; | |
87 | BUG_ON(count > (ssize_t)PAGE_SIZE); | |
88 | if (count >= 0) | |
89 | buffer->count = count; | |
90 | else | |
91 | ret = count; | |
92 | return ret; | |
93 | } | |
94 | ||
95 | ||
96 | /** | |
97 | * flush_read_buffer - push buffer to userspace. | |
98 | * @buffer: data buffer for file. | |
99 | * @userbuf: user-passed buffer. | |
100 | * @count: number of bytes requested. | |
101 | * @ppos: file position. | |
102 | * | |
103 | * Copy the buffer we filled in fill_read_buffer() to userspace. | |
104 | * This is done at the reader's leisure, copying and advancing | |
105 | * the amount they specify each time. | |
106 | * This may be called continuously until the buffer is empty. | |
107 | */ | |
108 | static int flush_read_buffer(struct sysfs_buffer * buffer, char __user * buf, | |
109 | size_t count, loff_t * ppos) | |
110 | { | |
111 | int error; | |
112 | ||
113 | if (*ppos > buffer->count) | |
114 | return 0; | |
115 | ||
116 | if (count > (buffer->count - *ppos)) | |
117 | count = buffer->count - *ppos; | |
118 | ||
119 | error = copy_to_user(buf,buffer->page + *ppos,count); | |
120 | if (!error) | |
121 | *ppos += count; | |
122 | return error ? -EFAULT : count; | |
123 | } | |
124 | ||
125 | /** | |
126 | * sysfs_read_file - read an attribute. | |
127 | * @file: file pointer. | |
128 | * @buf: buffer to fill. | |
129 | * @count: number of bytes to read. | |
130 | * @ppos: starting offset in file. | |
131 | * | |
132 | * Userspace wants to read an attribute file. The attribute descriptor | |
133 | * is in the file's ->d_fsdata. The target object is in the directory's | |
134 | * ->d_fsdata. | |
135 | * | |
136 | * We call fill_read_buffer() to allocate and fill the buffer from the | |
137 | * object's show() method exactly once (if the read is happening from | |
138 | * the beginning of the file). That should fill the entire buffer with | |
139 | * all the data the object has to offer for that attribute. | |
140 | * We then call flush_read_buffer() to copy the buffer to userspace | |
141 | * in the increments specified. | |
142 | */ | |
143 | ||
144 | static ssize_t | |
145 | sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) | |
146 | { | |
147 | struct sysfs_buffer * buffer = file->private_data; | |
148 | ssize_t retval = 0; | |
149 | ||
150 | down(&buffer->sem); | |
151 | if (buffer->needs_read_fill) { | |
152 | if ((retval = fill_read_buffer(file->f_dentry,buffer))) | |
153 | goto out; | |
154 | } | |
155 | pr_debug("%s: count = %d, ppos = %lld, buf = %s\n", | |
156 | __FUNCTION__,count,*ppos,buffer->page); | |
157 | retval = flush_read_buffer(buffer,buf,count,ppos); | |
158 | out: | |
159 | up(&buffer->sem); | |
160 | return retval; | |
161 | } | |
162 | ||
163 | ||
164 | /** | |
165 | * fill_write_buffer - copy buffer from userspace. | |
166 | * @buffer: data buffer for file. | |
167 | * @userbuf: data from user. | |
168 | * @count: number of bytes in @userbuf. | |
169 | * | |
170 | * Allocate @buffer->page if it hasn't been already, then | |
171 | * copy the user-supplied buffer into it. | |
172 | */ | |
173 | ||
174 | static int | |
175 | fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count) | |
176 | { | |
177 | int error; | |
178 | ||
179 | if (!buffer->page) | |
180 | buffer->page = (char *)get_zeroed_page(GFP_KERNEL); | |
181 | if (!buffer->page) | |
182 | return -ENOMEM; | |
183 | ||
184 | if (count >= PAGE_SIZE) | |
185 | count = PAGE_SIZE - 1; | |
186 | error = copy_from_user(buffer->page,buf,count); | |
187 | buffer->needs_read_fill = 1; | |
188 | return error ? -EFAULT : count; | |
189 | } | |
190 | ||
191 | ||
192 | /** | |
193 | * flush_write_buffer - push buffer to kobject. | |
194 | * @file: file pointer. | |
195 | * @buffer: data buffer for file. | |
196 | * | |
197 | * Get the correct pointers for the kobject and the attribute we're | |
198 | * dealing with, then call the store() method for the attribute, | |
199 | * passing the buffer that we acquired in fill_write_buffer(). | |
200 | */ | |
201 | ||
202 | static int | |
203 | flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count) | |
204 | { | |
205 | struct attribute * attr = to_attr(dentry); | |
206 | struct kobject * kobj = to_kobj(dentry->d_parent); | |
207 | struct sysfs_ops * ops = buffer->ops; | |
208 | ||
209 | return ops->store(kobj,attr,buffer->page,count); | |
210 | } | |
211 | ||
212 | ||
213 | /** | |
214 | * sysfs_write_file - write an attribute. | |
215 | * @file: file pointer | |
216 | * @buf: data to write | |
217 | * @count: number of bytes | |
218 | * @ppos: starting offset | |
219 | * | |
220 | * Similar to sysfs_read_file(), though working in the opposite direction. | |
221 | * We allocate and fill the data from the user in fill_write_buffer(), | |
222 | * then push it to the kobject in flush_write_buffer(). | |
223 | * There is no easy way for us to know if userspace is only doing a partial | |
224 | * write, so we don't support them. We expect the entire buffer to come | |
225 | * on the first write. | |
226 | * Hint: if you're writing a value, first read the file, modify only the | |
227 | * the value you're changing, then write entire buffer back. | |
228 | */ | |
229 | ||
230 | static ssize_t | |
231 | sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) | |
232 | { | |
233 | struct sysfs_buffer * buffer = file->private_data; | |
234 | ssize_t len; | |
235 | ||
236 | down(&buffer->sem); | |
237 | len = fill_write_buffer(buffer, buf, count); | |
238 | if (len > 0) | |
239 | len = flush_write_buffer(file->f_dentry, buffer, len); | |
240 | if (len > 0) | |
241 | *ppos += len; | |
242 | up(&buffer->sem); | |
243 | return len; | |
244 | } | |
245 | ||
246 | static int check_perm(struct inode * inode, struct file * file) | |
247 | { | |
248 | struct kobject *kobj = sysfs_get_kobject(file->f_dentry->d_parent); | |
249 | struct attribute * attr = to_attr(file->f_dentry); | |
250 | struct sysfs_buffer * buffer; | |
251 | struct sysfs_ops * ops = NULL; | |
252 | int error = 0; | |
253 | ||
254 | if (!kobj || !attr) | |
255 | goto Einval; | |
256 | ||
257 | /* Grab the module reference for this attribute if we have one */ | |
258 | if (!try_module_get(attr->owner)) { | |
259 | error = -ENODEV; | |
260 | goto Done; | |
261 | } | |
262 | ||
263 | /* if the kobject has no ktype, then we assume that it is a subsystem | |
264 | * itself, and use ops for it. | |
265 | */ | |
266 | if (kobj->kset && kobj->kset->ktype) | |
267 | ops = kobj->kset->ktype->sysfs_ops; | |
268 | else if (kobj->ktype) | |
269 | ops = kobj->ktype->sysfs_ops; | |
270 | else | |
271 | ops = &subsys_sysfs_ops; | |
272 | ||
273 | /* No sysfs operations, either from having no subsystem, | |
274 | * or the subsystem have no operations. | |
275 | */ | |
276 | if (!ops) | |
277 | goto Eaccess; | |
278 | ||
279 | /* File needs write support. | |
280 | * The inode's perms must say it's ok, | |
281 | * and we must have a store method. | |
282 | */ | |
283 | if (file->f_mode & FMODE_WRITE) { | |
284 | ||
285 | if (!(inode->i_mode & S_IWUGO) || !ops->store) | |
286 | goto Eaccess; | |
287 | ||
288 | } | |
289 | ||
290 | /* File needs read support. | |
291 | * The inode's perms must say it's ok, and we there | |
292 | * must be a show method for it. | |
293 | */ | |
294 | if (file->f_mode & FMODE_READ) { | |
295 | if (!(inode->i_mode & S_IRUGO) || !ops->show) | |
296 | goto Eaccess; | |
297 | } | |
298 | ||
299 | /* No error? Great, allocate a buffer for the file, and store it | |
300 | * it in file->private_data for easy access. | |
301 | */ | |
302 | buffer = kmalloc(sizeof(struct sysfs_buffer),GFP_KERNEL); | |
303 | if (buffer) { | |
304 | memset(buffer,0,sizeof(struct sysfs_buffer)); | |
305 | init_MUTEX(&buffer->sem); | |
306 | buffer->needs_read_fill = 1; | |
307 | buffer->ops = ops; | |
308 | file->private_data = buffer; | |
309 | } else | |
310 | error = -ENOMEM; | |
311 | goto Done; | |
312 | ||
313 | Einval: | |
314 | error = -EINVAL; | |
315 | goto Done; | |
316 | Eaccess: | |
317 | error = -EACCES; | |
318 | module_put(attr->owner); | |
319 | Done: | |
320 | if (error && kobj) | |
321 | kobject_put(kobj); | |
322 | return error; | |
323 | } | |
324 | ||
325 | static int sysfs_open_file(struct inode * inode, struct file * filp) | |
326 | { | |
327 | return check_perm(inode,filp); | |
328 | } | |
329 | ||
330 | static int sysfs_release(struct inode * inode, struct file * filp) | |
331 | { | |
332 | struct kobject * kobj = to_kobj(filp->f_dentry->d_parent); | |
333 | struct attribute * attr = to_attr(filp->f_dentry); | |
334 | struct module * owner = attr->owner; | |
335 | struct sysfs_buffer * buffer = filp->private_data; | |
336 | ||
337 | if (kobj) | |
338 | kobject_put(kobj); | |
339 | /* After this point, attr should not be accessed. */ | |
340 | module_put(owner); | |
341 | ||
342 | if (buffer) { | |
343 | if (buffer->page) | |
344 | free_page((unsigned long)buffer->page); | |
345 | kfree(buffer); | |
346 | } | |
347 | return 0; | |
348 | } | |
349 | ||
350 | struct file_operations sysfs_file_operations = { | |
351 | .read = sysfs_read_file, | |
352 | .write = sysfs_write_file, | |
353 | .llseek = generic_file_llseek, | |
354 | .open = sysfs_open_file, | |
355 | .release = sysfs_release, | |
356 | }; | |
357 | ||
358 | ||
359 | int sysfs_add_file(struct dentry * dir, const struct attribute * attr, int type) | |
360 | { | |
361 | struct sysfs_dirent * parent_sd = dir->d_fsdata; | |
362 | umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG; | |
363 | int error = 0; | |
364 | ||
365 | down(&dir->d_inode->i_sem); | |
366 | error = sysfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type); | |
367 | up(&dir->d_inode->i_sem); | |
368 | ||
369 | return error; | |
370 | } | |
371 | ||
372 | ||
373 | /** | |
374 | * sysfs_create_file - create an attribute file for an object. | |
375 | * @kobj: object we're creating for. | |
376 | * @attr: atrribute descriptor. | |
377 | */ | |
378 | ||
379 | int sysfs_create_file(struct kobject * kobj, const struct attribute * attr) | |
380 | { | |
381 | BUG_ON(!kobj || !kobj->dentry || !attr); | |
382 | ||
383 | return sysfs_add_file(kobj->dentry, attr, SYSFS_KOBJ_ATTR); | |
384 | ||
385 | } | |
386 | ||
387 | ||
388 | /** | |
389 | * sysfs_update_file - update the modified timestamp on an object attribute. | |
390 | * @kobj: object we're acting for. | |
391 | * @attr: attribute descriptor. | |
392 | * | |
393 | * Also call dnotify for the dentry, which lots of userspace programs | |
394 | * use. | |
395 | */ | |
396 | int sysfs_update_file(struct kobject * kobj, const struct attribute * attr) | |
397 | { | |
398 | struct dentry * dir = kobj->dentry; | |
399 | struct dentry * victim; | |
400 | int res = -ENOENT; | |
401 | ||
402 | down(&dir->d_inode->i_sem); | |
403 | victim = sysfs_get_dentry(dir, attr->name); | |
404 | if (!IS_ERR(victim)) { | |
405 | /* make sure dentry is really there */ | |
406 | if (victim->d_inode && | |
407 | (victim->d_parent->d_inode == dir->d_inode)) { | |
408 | victim->d_inode->i_mtime = CURRENT_TIME; | |
409 | dnotify_parent(victim, DN_MODIFY); | |
410 | ||
411 | /** | |
412 | * Drop reference from initial sysfs_get_dentry(). | |
413 | */ | |
414 | dput(victim); | |
415 | res = 0; | |
416 | } else | |
417 | d_drop(victim); | |
418 | ||
419 | /** | |
420 | * Drop the reference acquired from sysfs_get_dentry() above. | |
421 | */ | |
422 | dput(victim); | |
423 | } | |
424 | up(&dir->d_inode->i_sem); | |
425 | ||
426 | return res; | |
427 | } | |
428 | ||
429 | ||
430 | /** | |
431 | * sysfs_remove_file - remove an object attribute. | |
432 | * @kobj: object we're acting for. | |
433 | * @attr: attribute descriptor. | |
434 | * | |
435 | * Hash the attribute name and kill the victim. | |
436 | */ | |
437 | ||
438 | void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr) | |
439 | { | |
440 | sysfs_hash_and_remove(kobj->dentry,attr->name); | |
441 | } | |
442 | ||
443 | ||
444 | EXPORT_SYMBOL_GPL(sysfs_create_file); | |
445 | EXPORT_SYMBOL_GPL(sysfs_remove_file); | |
446 | EXPORT_SYMBOL_GPL(sysfs_update_file); | |
447 |