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 mutex_lock(&dir->d_inode->i_mutex); 340 error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type); 341 mutex_unlock(&dir->d_inode->i_mutex); 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 } 360 361