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7063fbf2 JB |
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 | 29 | #include <linux/slab.h> |
6d748924 | 30 | #include <linux/mutex.h> |
7063fbf2 | 31 | #include <asm/uaccess.h> |
7063fbf2 JB |
32 | |
33 | #include <linux/configfs.h> | |
34 | #include "configfs_internal.h" | |
35 | ||
b23cdde4 JB |
36 | /* |
37 | * A simple attribute can only be 4096 characters. Why 4k? Because the | |
38 | * original code limited it to PAGE_SIZE. That's a bad idea, though, | |
39 | * because an attribute of 16k on ia64 won't work on x86. So we limit to | |
40 | * 4k, our minimum common page size. | |
41 | */ | |
42 | #define SIMPLE_ATTR_SIZE 4096 | |
7063fbf2 JB |
43 | |
44 | struct configfs_buffer { | |
45 | size_t count; | |
46 | loff_t pos; | |
47 | char * page; | |
48 | struct configfs_item_operations * ops; | |
6d748924 | 49 | struct mutex mutex; |
7063fbf2 JB |
50 | int needs_read_fill; |
51 | }; | |
52 | ||
53 | ||
54 | /** | |
55 | * fill_read_buffer - allocate and fill buffer from item. | |
56 | * @dentry: dentry pointer. | |
57 | * @buffer: data buffer for file. | |
58 | * | |
59 | * Allocate @buffer->page, if it hasn't been already, then call the | |
60 | * config_item's show() method to fill the buffer with this attribute's | |
61 | * data. | |
62 | * This is called only once, on the file's first read. | |
63 | */ | |
64 | static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer) | |
65 | { | |
66 | struct configfs_attribute * attr = to_attr(dentry); | |
67 | struct config_item * item = to_item(dentry->d_parent); | |
7063fbf2 JB |
68 | int ret = 0; |
69 | ssize_t count; | |
70 | ||
71 | if (!buffer->page) | |
72 | buffer->page = (char *) get_zeroed_page(GFP_KERNEL); | |
73 | if (!buffer->page) | |
74 | return -ENOMEM; | |
75 | ||
51798222 | 76 | count = attr->show(item, buffer->page); |
870823e6 | 77 | |
7063fbf2 | 78 | buffer->needs_read_fill = 0; |
b23cdde4 | 79 | BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE); |
7063fbf2 JB |
80 | if (count >= 0) |
81 | buffer->count = count; | |
82 | else | |
83 | ret = count; | |
84 | return ret; | |
85 | } | |
86 | ||
7063fbf2 JB |
87 | /** |
88 | * configfs_read_file - read an attribute. | |
89 | * @file: file pointer. | |
90 | * @buf: buffer to fill. | |
91 | * @count: number of bytes to read. | |
92 | * @ppos: starting offset in file. | |
93 | * | |
94 | * Userspace wants to read an attribute file. The attribute descriptor | |
95 | * is in the file's ->d_fsdata. The target item is in the directory's | |
96 | * ->d_fsdata. | |
97 | * | |
98 | * We call fill_read_buffer() to allocate and fill the buffer from the | |
99 | * item's show() method exactly once (if the read is happening from | |
100 | * the beginning of the file). That should fill the entire buffer with | |
101 | * all the data the item has to offer for that attribute. | |
102 | * We then call flush_read_buffer() to copy the buffer to userspace | |
103 | * in the increments specified. | |
104 | */ | |
105 | ||
106 | static ssize_t | |
107 | configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) | |
108 | { | |
109 | struct configfs_buffer * buffer = file->private_data; | |
110 | ssize_t retval = 0; | |
111 | ||
6d748924 | 112 | mutex_lock(&buffer->mutex); |
7063fbf2 | 113 | if (buffer->needs_read_fill) { |
867fa491 | 114 | if ((retval = fill_read_buffer(file->f_path.dentry,buffer))) |
7063fbf2 JB |
115 | goto out; |
116 | } | |
4779efca | 117 | pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n", |
8e24eea7 | 118 | __func__, count, *ppos, buffer->page); |
92f4c701 AM |
119 | retval = simple_read_from_buffer(buf, count, ppos, buffer->page, |
120 | buffer->count); | |
7063fbf2 | 121 | out: |
6d748924 | 122 | mutex_unlock(&buffer->mutex); |
7063fbf2 JB |
123 | return retval; |
124 | } | |
125 | ||
126 | ||
127 | /** | |
128 | * fill_write_buffer - copy buffer from userspace. | |
129 | * @buffer: data buffer for file. | |
3d0f89bb | 130 | * @buf: data from user. |
7063fbf2 JB |
131 | * @count: number of bytes in @userbuf. |
132 | * | |
133 | * Allocate @buffer->page if it hasn't been already, then | |
134 | * copy the user-supplied buffer into it. | |
135 | */ | |
136 | ||
137 | static int | |
138 | fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count) | |
139 | { | |
140 | int error; | |
141 | ||
142 | if (!buffer->page) | |
ff05d1c4 | 143 | buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0); |
7063fbf2 JB |
144 | if (!buffer->page) |
145 | return -ENOMEM; | |
146 | ||
b23cdde4 JB |
147 | if (count >= SIMPLE_ATTR_SIZE) |
148 | count = SIMPLE_ATTR_SIZE - 1; | |
7063fbf2 JB |
149 | error = copy_from_user(buffer->page,buf,count); |
150 | buffer->needs_read_fill = 1; | |
ff05d1c4 JB |
151 | /* if buf is assumed to contain a string, terminate it by \0, |
152 | * so e.g. sscanf() can scan the string easily */ | |
153 | buffer->page[count] = 0; | |
7063fbf2 JB |
154 | return error ? -EFAULT : count; |
155 | } | |
156 | ||
157 | ||
158 | /** | |
159 | * flush_write_buffer - push buffer to config_item. | |
3d0f89bb | 160 | * @dentry: dentry to the attribute |
7063fbf2 | 161 | * @buffer: data buffer for file. |
3d0f89bb | 162 | * @count: number of bytes |
7063fbf2 JB |
163 | * |
164 | * Get the correct pointers for the config_item and the attribute we're | |
165 | * dealing with, then call the store() method for the attribute, | |
166 | * passing the buffer that we acquired in fill_write_buffer(). | |
167 | */ | |
168 | ||
169 | static int | |
170 | flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count) | |
171 | { | |
172 | struct configfs_attribute * attr = to_attr(dentry); | |
173 | struct config_item * item = to_item(dentry->d_parent); | |
7063fbf2 | 174 | |
870823e6 | 175 | return attr->store(item, buffer->page, count); |
7063fbf2 JB |
176 | } |
177 | ||
178 | ||
179 | /** | |
180 | * configfs_write_file - write an attribute. | |
181 | * @file: file pointer | |
182 | * @buf: data to write | |
183 | * @count: number of bytes | |
184 | * @ppos: starting offset | |
185 | * | |
186 | * Similar to configfs_read_file(), though working in the opposite direction. | |
187 | * We allocate and fill the data from the user in fill_write_buffer(), | |
188 | * then push it to the config_item in flush_write_buffer(). | |
189 | * There is no easy way for us to know if userspace is only doing a partial | |
190 | * write, so we don't support them. We expect the entire buffer to come | |
191 | * on the first write. | |
192 | * Hint: if you're writing a value, first read the file, modify only the | |
193 | * the value you're changing, then write entire buffer back. | |
194 | */ | |
195 | ||
196 | static ssize_t | |
197 | configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) | |
198 | { | |
199 | struct configfs_buffer * buffer = file->private_data; | |
3d0f89bb | 200 | ssize_t len; |
7063fbf2 | 201 | |
6d748924 | 202 | mutex_lock(&buffer->mutex); |
3d0f89bb JB |
203 | len = fill_write_buffer(buffer, buf, count); |
204 | if (len > 0) | |
7121064b | 205 | len = flush_write_buffer(file->f_path.dentry, buffer, len); |
3d0f89bb JB |
206 | if (len > 0) |
207 | *ppos += len; | |
6d748924 | 208 | mutex_unlock(&buffer->mutex); |
3d0f89bb | 209 | return len; |
7063fbf2 JB |
210 | } |
211 | ||
212 | static int check_perm(struct inode * inode, struct file * file) | |
213 | { | |
867fa491 JJS |
214 | struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent); |
215 | struct configfs_attribute * attr = to_attr(file->f_path.dentry); | |
7063fbf2 JB |
216 | struct configfs_buffer * buffer; |
217 | struct configfs_item_operations * ops = NULL; | |
218 | int error = 0; | |
219 | ||
220 | if (!item || !attr) | |
221 | goto Einval; | |
222 | ||
223 | /* Grab the module reference for this attribute if we have one */ | |
224 | if (!try_module_get(attr->ca_owner)) { | |
225 | error = -ENODEV; | |
226 | goto Done; | |
227 | } | |
228 | ||
229 | if (item->ci_type) | |
230 | ops = item->ci_type->ct_item_ops; | |
231 | else | |
232 | goto Eaccess; | |
233 | ||
234 | /* File needs write support. | |
235 | * The inode's perms must say it's ok, | |
236 | * and we must have a store method. | |
237 | */ | |
238 | if (file->f_mode & FMODE_WRITE) { | |
51798222 | 239 | if (!(inode->i_mode & S_IWUGO) || !attr->store) |
7063fbf2 JB |
240 | goto Eaccess; |
241 | ||
242 | } | |
243 | ||
244 | /* File needs read support. | |
245 | * The inode's perms must say it's ok, and we there | |
246 | * must be a show method for it. | |
247 | */ | |
248 | if (file->f_mode & FMODE_READ) { | |
51798222 | 249 | if (!(inode->i_mode & S_IRUGO) || !attr->show) |
7063fbf2 JB |
250 | goto Eaccess; |
251 | } | |
252 | ||
253 | /* No error? Great, allocate a buffer for the file, and store it | |
254 | * it in file->private_data for easy access. | |
255 | */ | |
f8314dc6 | 256 | buffer = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL); |
559c9ac3 | 257 | if (!buffer) { |
7063fbf2 | 258 | error = -ENOMEM; |
559c9ac3 CS |
259 | goto Enomem; |
260 | } | |
6d748924 | 261 | mutex_init(&buffer->mutex); |
559c9ac3 CS |
262 | buffer->needs_read_fill = 1; |
263 | buffer->ops = ops; | |
264 | file->private_data = buffer; | |
7063fbf2 JB |
265 | goto Done; |
266 | ||
267 | Einval: | |
268 | error = -EINVAL; | |
269 | goto Done; | |
270 | Eaccess: | |
271 | error = -EACCES; | |
559c9ac3 | 272 | Enomem: |
7063fbf2 JB |
273 | module_put(attr->ca_owner); |
274 | Done: | |
275 | if (error && item) | |
276 | config_item_put(item); | |
277 | return error; | |
278 | } | |
279 | ||
280 | static int configfs_open_file(struct inode * inode, struct file * filp) | |
281 | { | |
282 | return check_perm(inode,filp); | |
283 | } | |
284 | ||
285 | static int configfs_release(struct inode * inode, struct file * filp) | |
286 | { | |
867fa491 JJS |
287 | struct config_item * item = to_item(filp->f_path.dentry->d_parent); |
288 | struct configfs_attribute * attr = to_attr(filp->f_path.dentry); | |
7063fbf2 JB |
289 | struct module * owner = attr->ca_owner; |
290 | struct configfs_buffer * buffer = filp->private_data; | |
291 | ||
292 | if (item) | |
293 | config_item_put(item); | |
294 | /* After this point, attr should not be accessed. */ | |
295 | module_put(owner); | |
296 | ||
297 | if (buffer) { | |
298 | if (buffer->page) | |
299 | free_page((unsigned long)buffer->page); | |
6d748924 | 300 | mutex_destroy(&buffer->mutex); |
7063fbf2 JB |
301 | kfree(buffer); |
302 | } | |
303 | return 0; | |
304 | } | |
305 | ||
4b6f5d20 | 306 | const struct file_operations configfs_file_operations = { |
7063fbf2 JB |
307 | .read = configfs_read_file, |
308 | .write = configfs_write_file, | |
309 | .llseek = generic_file_llseek, | |
310 | .open = configfs_open_file, | |
311 | .release = configfs_release, | |
312 | }; | |
313 | ||
7063fbf2 JB |
314 | /** |
315 | * configfs_create_file - create an attribute file for an item. | |
316 | * @item: item we're creating for. | |
317 | * @attr: atrribute descriptor. | |
318 | */ | |
319 | ||
320 | int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr) | |
321 | { | |
28444a2b AV |
322 | struct dentry *dir = item->ci_dentry; |
323 | struct configfs_dirent *parent_sd = dir->d_fsdata; | |
324 | umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG; | |
325 | int error = 0; | |
7063fbf2 | 326 | |
2b0143b5 | 327 | mutex_lock_nested(&d_inode(dir)->i_mutex, I_MUTEX_NORMAL); |
28444a2b AV |
328 | error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, |
329 | CONFIGFS_ITEM_ATTR); | |
2b0143b5 | 330 | mutex_unlock(&d_inode(dir)->i_mutex); |
28444a2b AV |
331 | |
332 | return error; | |
7063fbf2 JB |
333 | } |
334 |