driver/device_driver.c

   1 /*
   2  *  SWAP device driver
   3  *  modules/driver/device_driver.c
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  18  *
  19  * Copyright (C) Samsung Electronics, 2013
  20  *
  21  * 2013  Alexander Aksenov <a.aksenov@samsung.com>: SWAP device driver implement
  22  *
  23  */
  24
  25 #include <linux/types.h>
  26 #include <linux/fs.h>
  27 #include <linux/cdev.h>
  28 #include <linux/err.h>
  29 #include <linux/device.h>
  30 #include <linux/ioctl.h>
  31 #include <linux/slab.h>
  32 #include <linux/mm.h>
  33 #include <linux/splice.h>
  34 #include <linux/sched.h>
  35 #include <linux/module.h>
  36 #include <linux/wait.h>
  37 #include <asm/uaccess.h>
  38
  39 #include <ksyms/ksyms.h>
  40
  41 #include "device_driver.h"
  42 #include "swap_driver_errors.h"
  43 #include "driver_to_buffer.h"
  44 #include "swap_ioctl.h"
  45 #include "driver_defs.h"
  46 #include "device_driver_to_driver_to_buffer.h"
  47 #include "driver_to_buffer.h"
  48 #include "driver_to_msg.h"
  49
  50 #define SWAP_DEVICE_NAME "swap_device"
  51
  52 /* swap_device driver routines */
  53 static int swap_device_open(struct inode *inode, struct file *filp);
  54 static int swap_device_release(struct inode *inode, struct file *file);
  55 static ssize_t swap_device_read(struct file *filp, char __user *buf,
  56                                                                 size_t count, loff_t *f_pos);
  57 static ssize_t swap_device_write(struct file *filp, const char __user *buf,
  58                                                                  size_t count, loff_t *f_pos);
  59 static long swap_device_ioctl(struct file *filp, unsigned int cmd,
  60                                                          unsigned long arg);
  61 static ssize_t swap_device_splice_read(struct file *filp, loff_t *ppos,
  62                                                                            struct pipe_inode_info *pipe, size_t len,
  63                                                                            unsigned int flags);
  64
  65 /* File operations structure */
  66 const struct file_operations swap_device_fops = {
  67         .read = swap_device_read,
  68         .write = swap_device_write,
  69         .open = swap_device_open,
  70         .release = swap_device_release,
  71         .unlocked_ioctl = swap_device_ioctl,
  72         .splice_read = swap_device_splice_read,
  73 };
  74
  75 /* Typedefs for splice_* funcs. Prototypes are for linux-3.8.6 */
  76 typedef ssize_t(*splice_to_pipe_p_t)(struct pipe_inode_info *pipe,
  77                                          struct splice_pipe_desc *spd);
  78 typedef int(*splice_grow_spd_p_t)(const struct pipe_inode_info *pipe,
  79                                         struct splice_pipe_desc *spd);
  80
  81 static splice_to_pipe_p_t splice_to_pipe_p = NULL;
  82 static splice_grow_spd_p_t splice_grow_spd_p = NULL;
  83
  84 static msg_handler_t msg_handler = NULL;
  85
  86 /* Device numbers */
  87 static dev_t swap_device_no = 0;
  88
  89 /* Device cdev struct */
  90 static struct cdev *swap_device_cdev = NULL;
  91
  92 /* Device class struct */
  93 static struct class *swap_device_class = NULL;
  94
  95 /* Device device struct */
  96 static struct device *swap_device_device = NULL;
  97
  98 /* Reading tasks queue */
  99 static DECLARE_WAIT_QUEUE_HEAD(swap_device_wait);
 100
 101 /* We need this realization of splice_shrink_spd() because of the its desing
 102  * frequent changes that I have encountered in custom kernels */
 103 void swap_device_splice_shrink_spd(struct pipe_inode_info *pipe,
 104                                    struct splice_pipe_desc *spd)
 105 {
 106         if (pipe->buffers <= PIPE_DEF_BUFFERS)
 107                 return;
 108
 109         kfree(spd->pages);
 110         kfree(spd->partial);
 111 }
 112
 113
 114 /* Register device TODO Think of permanent major */
 115 int swap_device_init(void)
 116 {
 117         int result;
 118
 119         /* Allocating device major and minor nums for swap_device */
 120         result = alloc_chrdev_region(&swap_device_no, 0, 1, SWAP_DEVICE_NAME);
 121         if (result < 0) {
 122                 print_crit("Major number allocation has failed\n");
 123                 result = -E_SD_ALLOC_CHRDEV_FAIL;
 124                 goto init_fail;
 125         }
 126
 127         /* Creating device class. Using IS_ERR, because class_create returns ERR_PTR
 128          * on error. */
 129         swap_device_class = class_create(THIS_MODULE, SWAP_DEVICE_NAME);
 130         if (IS_ERR(swap_device_class)) {
 131                 print_crit("Class creation has failed\n");
 132                 result = -E_SD_CLASS_CREATE_FAIL;
 133                 goto init_fail;
 134         }
 135
 136         /* Cdev allocation */
 137         swap_device_cdev = cdev_alloc();
 138         if (!swap_device_cdev) {
 139                 print_crit("Cdev structure allocation has failed\n");
 140                 result = -E_SD_CDEV_ALLOC_FAIL;
 141                 goto init_fail;
 142         }
 143
 144         /* Cdev intialization and setting file operations */
 145         cdev_init(swap_device_cdev, &swap_device_fops);
 146
 147         /* Adding cdev to system */
 148         result = cdev_add(swap_device_cdev, swap_device_no, 1);
 149         if (result < 0) {
 150                 print_crit("Device adding has failed\n");
 151                 result = -E_SD_CDEV_ADD_FAIL;
 152                 goto init_fail;
 153         }
 154
 155         /* Create device struct */
 156         swap_device_device = device_create(swap_device_class, NULL, swap_device_no,
 157                                                                            "%s", SWAP_DEVICE_NAME);
 158         if (IS_ERR(swap_device_device)) {
 159                 print_crit("Device struct creating has failed\n");
 160                 result = -E_SD_DEVICE_CREATE_FAIL;
 161                 goto init_fail;
 162         }
 163
 164         /* Find splice_* funcs addresses */
 165         splice_to_pipe_p = (splice_to_pipe_p_t)swap_ksyms("splice_to_pipe");
 166         if (!splice_to_pipe_p) {
 167                 print_err("splice_to_pipe() not found!\n");
 168                 result = -E_SD_NO_SPLICE_FUNCS;
 169                 goto init_fail;
 170         }
 171
 172         splice_grow_spd_p = (splice_grow_spd_p_t)swap_ksyms("splice_grow_spd");
 173         if (!splice_grow_spd_p) {
 174                 print_err("splice_grow_spd() not found!\n");
 175                 result = -E_SD_NO_SPLICE_FUNCS;
 176                 goto init_fail;
 177         }
 178
 179         return 0;
 180
 181 init_fail:
 182         if (swap_device_cdev) {
 183                 cdev_del(swap_device_cdev);
 184         }
 185         if (swap_device_class) {
 186                 class_destroy(swap_device_class);
 187         }
 188         if (swap_device_no) {
 189                 unregister_chrdev_region(swap_device_no, 1);
 190         }
 191         return result;
 192 }
 193
 194 /* Unregister device TODO Check wether driver is registered */
 195 void swap_device_exit(void)
 196 {
 197         splice_to_pipe_p = NULL;
 198         splice_grow_spd_p = NULL;
 199
 200         device_destroy(swap_device_class, swap_device_no);
 201         cdev_del(swap_device_cdev);
 202         class_destroy(swap_device_class);
 203         unregister_chrdev_region(swap_device_no, 1);
 204 }
 205
 206 static int swap_device_open(struct inode *inode, struct file *filp)
 207 {
 208         // TODO MOD_INC_USE_COUNT
 209         return 0;
 210 }
 211
 212 static int swap_device_release(struct inode *inode, struct file *filp)
 213 {
 214         // TODO MOD_DEC_USE_COUNT
 215         return 0;
 216 }
 217
 218 static ssize_t swap_device_read(struct file *filp, char __user *buf,
 219                                                                 size_t count, loff_t *f_pos)
 220 {
 221         /* Wait queue item that consists current task. It is used to be added in
 222          * swap_device_wait queue if there is no data to be read. */
 223         DEFINE_WAIT(wait);
 224         int result;
 225
 226         //TODO : Think about spin_locks to prevent reading race condition.
 227         while((result = driver_to_buffer_next_buffer_to_read()) != E_SD_SUCCESS) {
 228
 229                 /* Add process to the swap_device_wait queue and set the current task
 230                  * state TASK_INTERRUPTIBLE. If there is any data to be read, then the
 231                  * current task is removed from the swap_device_wait queue and its state
 232                  * is changed to this. */
 233                 prepare_to_wait(&swap_device_wait, &wait, TASK_INTERRUPTIBLE);
 234
 235                 if (result < 0) {
 236                         result = 0;
 237                         goto swap_device_read_error;
 238                 } else if (result == E_SD_NO_DATA_TO_READ) {
 239                         /* Yes, E_SD_NO_DATA_TO_READ should be positive, cause it's not
 240                          * really an error */
 241                         if (filp->f_flags & O_NONBLOCK) {
 242                                 result = -EAGAIN;
 243                                 goto swap_device_read_error;
 244                         }
 245                         if (signal_pending(current)) {
 246                                 result = -ERESTARTSYS;
 247                                 goto swap_device_read_error;
 248                         }
 249                         schedule();
 250                         finish_wait(&swap_device_wait, &wait);
 251                 }
 252         }
 253
 254         result = driver_to_buffer_read(buf, count);
 255         /* If there is an error - return 0 */
 256         if (result < 0)
 257                 result = 0;
 258
 259
 260         return result;
 261
 262 swap_device_read_error:
 263         finish_wait(&swap_device_wait, &wait);
 264
 265         return result;
 266 }
 267
 268 static ssize_t swap_device_write(struct file *filp, const char __user *buf,
 269                                                                  size_t count, loff_t *f_pos)
 270 {
 271         char *kern_buffer = NULL;
 272         ssize_t result = 0;
 273
 274         kern_buffer = kmalloc(count, GFP_KERNEL);
 275         if (!kern_buffer) {
 276                 print_err("Error allocating memory for buffer\n");
 277                 goto swap_device_write_out;
 278         }
 279
 280         result = copy_from_user(kern_buffer, buf, count);
 281
 282         result = count - result;
 283
 284         /* Return 0 if there was an error while writing */
 285         result = driver_to_buffer_write(result, kern_buffer);
 286         if (result < 0)
 287                 result = 0;
 288
 289         kfree(kern_buffer);
 290
 291 swap_device_write_out:
 292         return result;
 293 }
 294
 295 static long swap_device_ioctl(struct file *filp, unsigned int cmd,
 296                                                          unsigned long arg)
 297 {
 298         int result;
 299
 300         switch(cmd) {
 301                 case SWAP_DRIVER_BUFFER_INITIALIZE:
 302                 {
 303                         struct buffer_initialize initialize_struct;
 304
 305                         result = copy_from_user(&initialize_struct, (void*)arg,
 306                                                                         sizeof(struct buffer_initialize));
 307                         if (result) {
 308                                 break;
 309                         }
 310
 311                         result = driver_to_buffer_initialize(initialize_struct.size,
 312                                                                                                  initialize_struct.count);
 313                         if (result < 0) {
 314                                 print_err("Buffer initialization failed %d\n", result);
 315                                 break;
 316                         }
 317                         result = E_SD_SUCCESS;
 318
 319                         break;
 320                 }
 321                 case SWAP_DRIVER_BUFFER_UNINITIALIZE:
 322                 {
 323                         result = driver_to_buffer_uninitialize();
 324                         if (result < 0)
 325                         print_err("Buffer uninitialization failed %d\n", result);
 326
 327                         break;
 328                 }
 329                 case SWAP_DRIVER_NEXT_BUFFER_TO_READ:
 330                 {
 331                         /* Use this carefully */
 332                         result = driver_to_buffer_next_buffer_to_read();
 333                         if (result == E_SD_NO_DATA_TO_READ) {
 334                                 /* TODO Do what we usually do when there are no subbuffers to
 335                                  * read (make daemon sleep ?) */
 336                         }
 337                         break;
 338                 }
 339                 case SWAP_DRIVER_FLUSH_BUFFER:
 340                 {
 341                         result = driver_to_buffer_flush();
 342                         break;
 343                 }
 344                 case SWAP_DRIVER_MSG:
 345                         if (msg_handler) {
 346                                 result = msg_handler((void __user *)arg);
 347                         } else {
 348                                 print_warn("msg_handler() is not register\n");
 349                                 result = -EINVAL;
 350                         }
 351                         break;
 352                 default:
 353                         print_warn("Unknown command %d\n", cmd);
 354                         result = -EINVAL;
 355                         break;
 356
 357         }
 358         return result;
 359 }
 360
 361 static void swap_device_pipe_buf_release(struct pipe_inode_info *inode,
 362                                                                                  struct pipe_buffer *pipe)
 363 {
 364         __free_page(pipe->page);
 365 }
 366
 367 static void swap_device_page_release(struct splice_pipe_desc *spd,
 368                                                                          unsigned int i)
 369 {
 370         __free_page(spd->pages[i]);
 371 }
 372
 373 static const struct pipe_buf_operations swap_device_pipe_buf_ops = {
 374         .can_merge = 0,
 375         .map = generic_pipe_buf_map,
 376         .unmap = generic_pipe_buf_unmap,
 377         .confirm = generic_pipe_buf_confirm,
 378         .release = swap_device_pipe_buf_release,
 379         .steal = generic_pipe_buf_steal,
 380         .get = generic_pipe_buf_get
 381 };
 382
 383 static ssize_t swap_device_splice_read(struct file *filp, loff_t *ppos,
 384                                                                            struct pipe_inode_info *pipe,
 385                                                                            size_t len, unsigned int flags)
 386 {
 387         /* Wait queue item that consists current task. It is used to be added in
 388          * swap_device_wait queue if there is no data to be read. */
 389         DEFINE_WAIT(wait);
 390
 391         int result;
 392         struct page *pages[PIPE_DEF_BUFFERS];
 393         struct partial_page partial[PIPE_DEF_BUFFERS];
 394         struct splice_pipe_desc spd = {
 395                 .pages = pages,
 396                 .partial = partial,
 397 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 4, 5))
 398                 .nr_pages_max = PIPE_DEF_BUFFERS,
 399 #endif
 400                 .nr_pages = 0,
 401                 .flags = flags,
 402                 .ops = &swap_device_pipe_buf_ops,
 403                 .spd_release = swap_device_page_release,
 404         };
 405
 406         /* Get next buffer to read */
 407         //TODO : Think about spin_locks to prevent reading race condition.
 408         while((result = driver_to_buffer_next_buffer_to_read()) != E_SD_SUCCESS) {
 409
 410                 /* Add process to the swap_device_wait queue and set the current task
 411                  * state TASK_INTERRUPTIBLE. If there is any data to be read, then the
 412                  * current task is removed from the swap_device_wait queue and its state
 413                  * is changed. */
 414                 prepare_to_wait(&swap_device_wait, &wait, TASK_INTERRUPTIBLE);
 415                 if (result < 0) {
 416                         print_err("driver_to_buffer_next_buffer_to_read error %d\n", result);
 417                         //TODO Error return to OS
 418                         result = 0;
 419                         goto swap_device_splice_read_error;
 420                 } else if (result == E_SD_NO_DATA_TO_READ) {
 421                         if (filp->f_flags & O_NONBLOCK) {
 422                                 result = -EAGAIN;
 423                                 goto swap_device_splice_read_error;
 424                         }
 425                         if (signal_pending(current)) {
 426                                 result = -ERESTARTSYS;
 427                                 goto swap_device_splice_read_error;
 428                         }
 429                         schedule();
 430                         finish_wait(&swap_device_wait, &wait);
 431                 }
 432         }
 433
 434         if (splice_grow_spd_p(pipe, &spd)) {
 435                 result = -ENOMEM;
 436                 goto swap_device_splice_read_out;
 437         }
 438
 439         result = driver_to_buffer_fill_spd(&spd);
 440         if (result != 0) {
 441                 print_err("Cannot fill spd for splice\n");
 442                 goto swap_device_shrink_spd;
 443         }
 444
 445         result = splice_to_pipe_p(pipe, &spd);
 446
 447 swap_device_shrink_spd:
 448         swap_device_splice_shrink_spd(pipe, &spd);
 449
 450 swap_device_splice_read_out:
 451         return result;
 452
 453 swap_device_splice_read_error:
 454         finish_wait(&swap_device_wait, &wait);
 455
 456         return result;
 457 }
 458
 459 void swap_device_wake_up_process(void)
 460 {
 461         wake_up_interruptible(&swap_device_wait);
 462 }
 463
 464 void set_msg_handler(msg_handler_t mh)
 465 {
 466         msg_handler = mh;
 467 }
 468 EXPORT_SYMBOL_GPL(set_msg_handler);