Joel Becker | 7063fbf | 2005-12-15 14:29:43 -0800 | [diff] [blame] | 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> |
| 29 | #include <linux/dnotify.h> |
| 30 | #include <linux/slab.h> |
| 31 | #include <asm/uaccess.h> |
| 32 | #include <asm/semaphore.h> |
| 33 | |
| 34 | #include <linux/configfs.h> |
| 35 | #include "configfs_internal.h" |
| 36 | |
| 37 | |
| 38 | struct configfs_buffer { |
| 39 | size_t count; |
| 40 | loff_t pos; |
| 41 | char * page; |
| 42 | struct configfs_item_operations * ops; |
| 43 | struct semaphore sem; |
| 44 | int needs_read_fill; |
| 45 | }; |
| 46 | |
| 47 | |
| 48 | /** |
| 49 | * fill_read_buffer - allocate and fill buffer from item. |
| 50 | * @dentry: dentry pointer. |
| 51 | * @buffer: data buffer for file. |
| 52 | * |
| 53 | * Allocate @buffer->page, if it hasn't been already, then call the |
| 54 | * config_item's show() method to fill the buffer with this attribute's |
| 55 | * data. |
| 56 | * This is called only once, on the file's first read. |
| 57 | */ |
| 58 | static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer) |
| 59 | { |
| 60 | struct configfs_attribute * attr = to_attr(dentry); |
| 61 | struct config_item * item = to_item(dentry->d_parent); |
| 62 | struct configfs_item_operations * ops = buffer->ops; |
| 63 | int ret = 0; |
| 64 | ssize_t count; |
| 65 | |
| 66 | if (!buffer->page) |
| 67 | buffer->page = (char *) get_zeroed_page(GFP_KERNEL); |
| 68 | if (!buffer->page) |
| 69 | return -ENOMEM; |
| 70 | |
| 71 | count = ops->show_attribute(item,attr,buffer->page); |
| 72 | buffer->needs_read_fill = 0; |
| 73 | BUG_ON(count > (ssize_t)PAGE_SIZE); |
| 74 | if (count >= 0) |
| 75 | buffer->count = count; |
| 76 | else |
| 77 | ret = count; |
| 78 | return ret; |
| 79 | } |
| 80 | |
| 81 | |
| 82 | /** |
| 83 | * flush_read_buffer - push buffer to userspace. |
| 84 | * @buffer: data buffer for file. |
| 85 | * @userbuf: user-passed buffer. |
| 86 | * @count: number of bytes requested. |
| 87 | * @ppos: file position. |
| 88 | * |
| 89 | * Copy the buffer we filled in fill_read_buffer() to userspace. |
| 90 | * This is done at the reader's leisure, copying and advancing |
| 91 | * the amount they specify each time. |
| 92 | * This may be called continuously until the buffer is empty. |
| 93 | */ |
| 94 | static int flush_read_buffer(struct configfs_buffer * buffer, char __user * buf, |
| 95 | size_t count, loff_t * ppos) |
| 96 | { |
| 97 | int error; |
| 98 | |
| 99 | if (*ppos > buffer->count) |
| 100 | return 0; |
| 101 | |
| 102 | if (count > (buffer->count - *ppos)) |
| 103 | count = buffer->count - *ppos; |
| 104 | |
| 105 | error = copy_to_user(buf,buffer->page + *ppos,count); |
| 106 | if (!error) |
| 107 | *ppos += count; |
| 108 | return error ? -EFAULT : count; |
| 109 | } |
| 110 | |
| 111 | /** |
| 112 | * configfs_read_file - read an attribute. |
| 113 | * @file: file pointer. |
| 114 | * @buf: buffer to fill. |
| 115 | * @count: number of bytes to read. |
| 116 | * @ppos: starting offset in file. |
| 117 | * |
| 118 | * Userspace wants to read an attribute file. The attribute descriptor |
| 119 | * is in the file's ->d_fsdata. The target item is in the directory's |
| 120 | * ->d_fsdata. |
| 121 | * |
| 122 | * We call fill_read_buffer() to allocate and fill the buffer from the |
| 123 | * item's show() method exactly once (if the read is happening from |
| 124 | * the beginning of the file). That should fill the entire buffer with |
| 125 | * all the data the item has to offer for that attribute. |
| 126 | * We then call flush_read_buffer() to copy the buffer to userspace |
| 127 | * in the increments specified. |
| 128 | */ |
| 129 | |
| 130 | static ssize_t |
| 131 | configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) |
| 132 | { |
| 133 | struct configfs_buffer * buffer = file->private_data; |
| 134 | ssize_t retval = 0; |
| 135 | |
| 136 | down(&buffer->sem); |
| 137 | if (buffer->needs_read_fill) { |
| 138 | if ((retval = fill_read_buffer(file->f_dentry,buffer))) |
| 139 | goto out; |
| 140 | } |
| 141 | pr_debug("%s: count = %d, ppos = %lld, buf = %s\n", |
| 142 | __FUNCTION__,count,*ppos,buffer->page); |
| 143 | retval = flush_read_buffer(buffer,buf,count,ppos); |
| 144 | out: |
| 145 | up(&buffer->sem); |
| 146 | return retval; |
| 147 | } |
| 148 | |
| 149 | |
| 150 | /** |
| 151 | * fill_write_buffer - copy buffer from userspace. |
| 152 | * @buffer: data buffer for file. |
| 153 | * @userbuf: data from user. |
| 154 | * @count: number of bytes in @userbuf. |
| 155 | * |
| 156 | * Allocate @buffer->page if it hasn't been already, then |
| 157 | * copy the user-supplied buffer into it. |
| 158 | */ |
| 159 | |
| 160 | static int |
| 161 | fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count) |
| 162 | { |
| 163 | int error; |
| 164 | |
| 165 | if (!buffer->page) |
| 166 | buffer->page = (char *)get_zeroed_page(GFP_KERNEL); |
| 167 | if (!buffer->page) |
| 168 | return -ENOMEM; |
| 169 | |
| 170 | if (count > PAGE_SIZE) |
| 171 | count = PAGE_SIZE; |
| 172 | error = copy_from_user(buffer->page,buf,count); |
| 173 | buffer->needs_read_fill = 1; |
| 174 | return error ? -EFAULT : count; |
| 175 | } |
| 176 | |
| 177 | |
| 178 | /** |
| 179 | * flush_write_buffer - push buffer to config_item. |
| 180 | * @file: file pointer. |
| 181 | * @buffer: data buffer for file. |
| 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; |
| 220 | |
| 221 | down(&buffer->sem); |
| 222 | count = fill_write_buffer(buffer,buf,count); |
| 223 | if (count > 0) |
| 224 | count = flush_write_buffer(file->f_dentry,buffer,count); |
| 225 | if (count > 0) |
| 226 | *ppos += count; |
| 227 | up(&buffer->sem); |
| 228 | return count; |
| 229 | } |
| 230 | |
| 231 | static int check_perm(struct inode * inode, struct file * file) |
| 232 | { |
| 233 | struct config_item *item = configfs_get_config_item(file->f_dentry->d_parent); |
| 234 | struct configfs_attribute * attr = to_attr(file->f_dentry); |
| 235 | struct configfs_buffer * buffer; |
| 236 | struct configfs_item_operations * ops = NULL; |
| 237 | int error = 0; |
| 238 | |
| 239 | if (!item || !attr) |
| 240 | goto Einval; |
| 241 | |
| 242 | /* Grab the module reference for this attribute if we have one */ |
| 243 | if (!try_module_get(attr->ca_owner)) { |
| 244 | error = -ENODEV; |
| 245 | goto Done; |
| 246 | } |
| 247 | |
| 248 | if (item->ci_type) |
| 249 | ops = item->ci_type->ct_item_ops; |
| 250 | else |
| 251 | goto Eaccess; |
| 252 | |
| 253 | /* File needs write support. |
| 254 | * The inode's perms must say it's ok, |
| 255 | * and we must have a store method. |
| 256 | */ |
| 257 | if (file->f_mode & FMODE_WRITE) { |
| 258 | |
| 259 | if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute) |
| 260 | goto Eaccess; |
| 261 | |
| 262 | } |
| 263 | |
| 264 | /* File needs read support. |
| 265 | * The inode's perms must say it's ok, and we there |
| 266 | * must be a show method for it. |
| 267 | */ |
| 268 | if (file->f_mode & FMODE_READ) { |
| 269 | if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute) |
| 270 | goto Eaccess; |
| 271 | } |
| 272 | |
| 273 | /* No error? Great, allocate a buffer for the file, and store it |
| 274 | * it in file->private_data for easy access. |
| 275 | */ |
| 276 | buffer = kmalloc(sizeof(struct configfs_buffer),GFP_KERNEL); |
| 277 | if (buffer) { |
| 278 | memset(buffer,0,sizeof(struct configfs_buffer)); |
| 279 | init_MUTEX(&buffer->sem); |
| 280 | buffer->needs_read_fill = 1; |
| 281 | buffer->ops = ops; |
| 282 | file->private_data = buffer; |
| 283 | } else |
| 284 | error = -ENOMEM; |
| 285 | goto Done; |
| 286 | |
| 287 | Einval: |
| 288 | error = -EINVAL; |
| 289 | goto Done; |
| 290 | Eaccess: |
| 291 | error = -EACCES; |
| 292 | module_put(attr->ca_owner); |
| 293 | Done: |
| 294 | if (error && item) |
| 295 | config_item_put(item); |
| 296 | return error; |
| 297 | } |
| 298 | |
| 299 | static int configfs_open_file(struct inode * inode, struct file * filp) |
| 300 | { |
| 301 | return check_perm(inode,filp); |
| 302 | } |
| 303 | |
| 304 | static int configfs_release(struct inode * inode, struct file * filp) |
| 305 | { |
| 306 | struct config_item * item = to_item(filp->f_dentry->d_parent); |
| 307 | struct configfs_attribute * attr = to_attr(filp->f_dentry); |
| 308 | struct module * owner = attr->ca_owner; |
| 309 | struct configfs_buffer * buffer = filp->private_data; |
| 310 | |
| 311 | if (item) |
| 312 | config_item_put(item); |
| 313 | /* After this point, attr should not be accessed. */ |
| 314 | module_put(owner); |
| 315 | |
| 316 | if (buffer) { |
| 317 | if (buffer->page) |
| 318 | free_page((unsigned long)buffer->page); |
| 319 | kfree(buffer); |
| 320 | } |
| 321 | return 0; |
| 322 | } |
| 323 | |
| 324 | struct file_operations configfs_file_operations = { |
| 325 | .read = configfs_read_file, |
| 326 | .write = configfs_write_file, |
| 327 | .llseek = generic_file_llseek, |
| 328 | .open = configfs_open_file, |
| 329 | .release = configfs_release, |
| 330 | }; |
| 331 | |
| 332 | |
| 333 | int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type) |
| 334 | { |
| 335 | struct configfs_dirent * parent_sd = dir->d_fsdata; |
| 336 | umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG; |
| 337 | int error = 0; |
| 338 | |
| 339 | down(&dir->d_inode->i_sem); |
| 340 | error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type); |
| 341 | up(&dir->d_inode->i_sem); |
| 342 | |
| 343 | return error; |
| 344 | } |
| 345 | |
| 346 | |
| 347 | /** |
| 348 | * configfs_create_file - create an attribute file for an item. |
| 349 | * @item: item we're creating for. |
| 350 | * @attr: atrribute descriptor. |
| 351 | */ |
| 352 | |
| 353 | int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr) |
| 354 | { |
| 355 | BUG_ON(!item || !item->ci_dentry || !attr); |
| 356 | |
| 357 | return configfs_add_file(item->ci_dentry, attr, |
| 358 | CONFIGFS_ITEM_ATTR); |
| 359 | } |
| 360 | |