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1 | /* -*- mode: c; c-basic-offset: 8; -*- |
2 | * vim: noexpandtab sw=8 ts=8 sts=0: | |
3 | * | |
4 | * file.c - operations for regular (text) files. | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public | |
8 | * License as published by the Free Software Foundation; either | |
9 | * version 2 of the License, or (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public | |
17 | * License along with this program; if not, write to the | |
18 | * Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
19 | * Boston, MA 021110-1307, USA. | |
20 | * | |
21 | * Based on sysfs: | |
22 | * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel | |
23 | * | |
24 | * configfs Copyright (C) 2005 Oracle. All rights reserved. | |
25 | */ | |
26 | ||
27 | #include <linux/fs.h> | |
28 | #include <linux/module.h> | |
7063fbf2 JB |
29 | #include <linux/slab.h> |
30 | #include <asm/uaccess.h> | |
31 | #include <asm/semaphore.h> | |
32 | ||
33 | #include <linux/configfs.h> | |
34 | #include "configfs_internal.h" | |
35 | ||
36 | ||
37 | struct configfs_buffer { | |
38 | size_t count; | |
39 | loff_t pos; | |
40 | char * page; | |
41 | struct configfs_item_operations * ops; | |
42 | struct semaphore sem; | |
43 | int needs_read_fill; | |
44 | }; | |
45 | ||
46 | ||
47 | /** | |
48 | * fill_read_buffer - allocate and fill buffer from item. | |
49 | * @dentry: dentry pointer. | |
50 | * @buffer: data buffer for file. | |
51 | * | |
52 | * Allocate @buffer->page, if it hasn't been already, then call the | |
53 | * config_item's show() method to fill the buffer with this attribute's | |
54 | * data. | |
55 | * This is called only once, on the file's first read. | |
56 | */ | |
57 | static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer) | |
58 | { | |
59 | struct configfs_attribute * attr = to_attr(dentry); | |
60 | struct config_item * item = to_item(dentry->d_parent); | |
61 | struct configfs_item_operations * ops = buffer->ops; | |
62 | int ret = 0; | |
63 | ssize_t count; | |
64 | ||
65 | if (!buffer->page) | |
66 | buffer->page = (char *) get_zeroed_page(GFP_KERNEL); | |
67 | if (!buffer->page) | |
68 | return -ENOMEM; | |
69 | ||
70 | count = ops->show_attribute(item,attr,buffer->page); | |
71 | buffer->needs_read_fill = 0; | |
72 | BUG_ON(count > (ssize_t)PAGE_SIZE); | |
73 | if (count >= 0) | |
74 | buffer->count = count; | |
75 | else | |
76 | ret = count; | |
77 | return ret; | |
78 | } | |
79 | ||
80 | ||
81 | /** | |
82 | * flush_read_buffer - push buffer to userspace. | |
83 | * @buffer: data buffer for file. | |
84 | * @userbuf: user-passed buffer. | |
85 | * @count: number of bytes requested. | |
86 | * @ppos: file position. | |
87 | * | |
88 | * Copy the buffer we filled in fill_read_buffer() to userspace. | |
89 | * This is done at the reader's leisure, copying and advancing | |
90 | * the amount they specify each time. | |
91 | * This may be called continuously until the buffer is empty. | |
92 | */ | |
93 | static int flush_read_buffer(struct configfs_buffer * buffer, char __user * buf, | |
94 | size_t count, loff_t * ppos) | |
95 | { | |
96 | int error; | |
97 | ||
98 | if (*ppos > buffer->count) | |
99 | return 0; | |
100 | ||
101 | if (count > (buffer->count - *ppos)) | |
102 | count = buffer->count - *ppos; | |
103 | ||
104 | error = copy_to_user(buf,buffer->page + *ppos,count); | |
105 | if (!error) | |
106 | *ppos += count; | |
107 | return error ? -EFAULT : count; | |
108 | } | |
109 | ||
110 | /** | |
111 | * configfs_read_file - read an attribute. | |
112 | * @file: file pointer. | |
113 | * @buf: buffer to fill. | |
114 | * @count: number of bytes to read. | |
115 | * @ppos: starting offset in file. | |
116 | * | |
117 | * Userspace wants to read an attribute file. The attribute descriptor | |
118 | * is in the file's ->d_fsdata. The target item is in the directory's | |
119 | * ->d_fsdata. | |
120 | * | |
121 | * We call fill_read_buffer() to allocate and fill the buffer from the | |
122 | * item's show() method exactly once (if the read is happening from | |
123 | * the beginning of the file). That should fill the entire buffer with | |
124 | * all the data the item has to offer for that attribute. | |
125 | * We then call flush_read_buffer() to copy the buffer to userspace | |
126 | * in the increments specified. | |
127 | */ | |
128 | ||
129 | static ssize_t | |
130 | configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) | |
131 | { | |
132 | struct configfs_buffer * buffer = file->private_data; | |
133 | ssize_t retval = 0; | |
134 | ||
135 | down(&buffer->sem); | |
136 | if (buffer->needs_read_fill) { | |
137 | if ((retval = fill_read_buffer(file->f_dentry,buffer))) | |
138 | goto out; | |
139 | } | |
140 | pr_debug("%s: count = %d, ppos = %lld, buf = %s\n", | |
141 | __FUNCTION__,count,*ppos,buffer->page); | |
142 | retval = flush_read_buffer(buffer,buf,count,ppos); | |
143 | out: | |
144 | up(&buffer->sem); | |
145 | return retval; | |
146 | } | |
147 | ||
148 | ||
149 | /** | |
150 | * fill_write_buffer - copy buffer from userspace. | |
151 | * @buffer: data buffer for file. | |
3d0f89bb | 152 | * @buf: data from user. |
7063fbf2 JB |
153 | * @count: number of bytes in @userbuf. |
154 | * | |
155 | * Allocate @buffer->page if it hasn't been already, then | |
156 | * copy the user-supplied buffer into it. | |
157 | */ | |
158 | ||
159 | static int | |
160 | fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count) | |
161 | { | |
162 | int error; | |
163 | ||
164 | if (!buffer->page) | |
165 | buffer->page = (char *)get_zeroed_page(GFP_KERNEL); | |
166 | if (!buffer->page) | |
167 | return -ENOMEM; | |
168 | ||
169 | if (count > PAGE_SIZE) | |
170 | count = PAGE_SIZE; | |
171 | error = copy_from_user(buffer->page,buf,count); | |
172 | buffer->needs_read_fill = 1; | |
173 | return error ? -EFAULT : count; | |
174 | } | |
175 | ||
176 | ||
177 | /** | |
178 | * flush_write_buffer - push buffer to config_item. | |
3d0f89bb | 179 | * @dentry: dentry to the attribute |
7063fbf2 | 180 | * @buffer: data buffer for file. |
3d0f89bb | 181 | * @count: number of bytes |
7063fbf2 JB |
182 | * |
183 | * Get the correct pointers for the config_item and the attribute we're | |
184 | * dealing with, then call the store() method for the attribute, | |
185 | * passing the buffer that we acquired in fill_write_buffer(). | |
186 | */ | |
187 | ||
188 | static int | |
189 | flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count) | |
190 | { | |
191 | struct configfs_attribute * attr = to_attr(dentry); | |
192 | struct config_item * item = to_item(dentry->d_parent); | |
193 | struct configfs_item_operations * ops = buffer->ops; | |
194 | ||
195 | return ops->store_attribute(item,attr,buffer->page,count); | |
196 | } | |
197 | ||
198 | ||
199 | /** | |
200 | * configfs_write_file - write an attribute. | |
201 | * @file: file pointer | |
202 | * @buf: data to write | |
203 | * @count: number of bytes | |
204 | * @ppos: starting offset | |
205 | * | |
206 | * Similar to configfs_read_file(), though working in the opposite direction. | |
207 | * We allocate and fill the data from the user in fill_write_buffer(), | |
208 | * then push it to the config_item in flush_write_buffer(). | |
209 | * There is no easy way for us to know if userspace is only doing a partial | |
210 | * write, so we don't support them. We expect the entire buffer to come | |
211 | * on the first write. | |
212 | * Hint: if you're writing a value, first read the file, modify only the | |
213 | * the value you're changing, then write entire buffer back. | |
214 | */ | |
215 | ||
216 | static ssize_t | |
217 | configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) | |
218 | { | |
219 | struct configfs_buffer * buffer = file->private_data; | |
3d0f89bb | 220 | ssize_t len; |
7063fbf2 JB |
221 | |
222 | down(&buffer->sem); | |
3d0f89bb JB |
223 | len = fill_write_buffer(buffer, buf, count); |
224 | if (len > 0) | |
225 | len = flush_write_buffer(file->f_dentry, buffer, count); | |
226 | if (len > 0) | |
227 | *ppos += len; | |
7063fbf2 | 228 | up(&buffer->sem); |
3d0f89bb | 229 | return len; |
7063fbf2 JB |
230 | } |
231 | ||
232 | static int check_perm(struct inode * inode, struct file * file) | |
233 | { | |
234 | struct config_item *item = configfs_get_config_item(file->f_dentry->d_parent); | |
235 | struct configfs_attribute * attr = to_attr(file->f_dentry); | |
236 | struct configfs_buffer * buffer; | |
237 | struct configfs_item_operations * ops = NULL; | |
238 | int error = 0; | |
239 | ||
240 | if (!item || !attr) | |
241 | goto Einval; | |
242 | ||
243 | /* Grab the module reference for this attribute if we have one */ | |
244 | if (!try_module_get(attr->ca_owner)) { | |
245 | error = -ENODEV; | |
246 | goto Done; | |
247 | } | |
248 | ||
249 | if (item->ci_type) | |
250 | ops = item->ci_type->ct_item_ops; | |
251 | else | |
252 | goto Eaccess; | |
253 | ||
254 | /* File needs write support. | |
255 | * The inode's perms must say it's ok, | |
256 | * and we must have a store method. | |
257 | */ | |
258 | if (file->f_mode & FMODE_WRITE) { | |
259 | ||
260 | if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute) | |
261 | goto Eaccess; | |
262 | ||
263 | } | |
264 | ||
265 | /* File needs read support. | |
266 | * The inode's perms must say it's ok, and we there | |
267 | * must be a show method for it. | |
268 | */ | |
269 | if (file->f_mode & FMODE_READ) { | |
270 | if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute) | |
271 | goto Eaccess; | |
272 | } | |
273 | ||
274 | /* No error? Great, allocate a buffer for the file, and store it | |
275 | * it in file->private_data for easy access. | |
276 | */ | |
277 | buffer = kmalloc(sizeof(struct configfs_buffer),GFP_KERNEL); | |
278 | if (buffer) { | |
279 | memset(buffer,0,sizeof(struct configfs_buffer)); | |
280 | init_MUTEX(&buffer->sem); | |
281 | buffer->needs_read_fill = 1; | |
282 | buffer->ops = ops; | |
283 | file->private_data = buffer; | |
284 | } else | |
285 | error = -ENOMEM; | |
286 | goto Done; | |
287 | ||
288 | Einval: | |
289 | error = -EINVAL; | |
290 | goto Done; | |
291 | Eaccess: | |
292 | error = -EACCES; | |
293 | module_put(attr->ca_owner); | |
294 | Done: | |
295 | if (error && item) | |
296 | config_item_put(item); | |
297 | return error; | |
298 | } | |
299 | ||
300 | static int configfs_open_file(struct inode * inode, struct file * filp) | |
301 | { | |
302 | return check_perm(inode,filp); | |
303 | } | |
304 | ||
305 | static int configfs_release(struct inode * inode, struct file * filp) | |
306 | { | |
307 | struct config_item * item = to_item(filp->f_dentry->d_parent); | |
308 | struct configfs_attribute * attr = to_attr(filp->f_dentry); | |
309 | struct module * owner = attr->ca_owner; | |
310 | struct configfs_buffer * buffer = filp->private_data; | |
311 | ||
312 | if (item) | |
313 | config_item_put(item); | |
314 | /* After this point, attr should not be accessed. */ | |
315 | module_put(owner); | |
316 | ||
317 | if (buffer) { | |
318 | if (buffer->page) | |
319 | free_page((unsigned long)buffer->page); | |
320 | kfree(buffer); | |
321 | } | |
322 | return 0; | |
323 | } | |
324 | ||
4b6f5d20 | 325 | const struct file_operations configfs_file_operations = { |
7063fbf2 JB |
326 | .read = configfs_read_file, |
327 | .write = configfs_write_file, | |
328 | .llseek = generic_file_llseek, | |
329 | .open = configfs_open_file, | |
330 | .release = configfs_release, | |
331 | }; | |
332 | ||
333 | ||
334 | int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type) | |
335 | { | |
336 | struct configfs_dirent * parent_sd = dir->d_fsdata; | |
337 | umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG; | |
338 | int error = 0; | |
339 | ||
1b1dcc1b | 340 | mutex_lock(&dir->d_inode->i_mutex); |
7063fbf2 | 341 | error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type); |
1b1dcc1b | 342 | mutex_unlock(&dir->d_inode->i_mutex); |
7063fbf2 JB |
343 | |
344 | return error; | |
345 | } | |
346 | ||
347 | ||
348 | /** | |
349 | * configfs_create_file - create an attribute file for an item. | |
350 | * @item: item we're creating for. | |
351 | * @attr: atrribute descriptor. | |
352 | */ | |
353 | ||
354 | int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr) | |
355 | { | |
356 | BUG_ON(!item || !item->ci_dentry || !attr); | |
357 | ||
358 | return configfs_add_file(item->ci_dentry, attr, | |
359 | CONFIGFS_ITEM_ATTR); | |
360 | } | |
361 |