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 <linux/workqueue.h>
  38 #include <asm/uaccess.h>
  39
  40 #include <ksyms/ksyms.h>
  41
  42 #include "device_driver.h"
  43 #include "swap_driver_errors.h"
  44 #include "driver_to_buffer.h"
  45 #include "swap_ioctl.h"
  46 #include "driver_defs.h"
  47 #include "device_driver_to_driver_to_buffer.h"
  48 #include "driver_to_buffer.h"
  49 #include "driver_to_msg.h"
  50
  51 #define SWAP_DEVICE_NAME "swap_device"
  52
  53 /* swap_device driver routines */
  54 static int swap_device_open(struct inode *inode, struct file *filp);
  55 static int swap_device_release(struct inode *inode, struct file *file);
  56 static ssize_t swap_device_read(struct file *filp, char __user *buf,
  57                                                                 size_t count, loff_t *f_pos);
  58 static long swap_device_ioctl(struct file *filp, unsigned int cmd,
  59                                                          unsigned long arg);
  60 static ssize_t swap_device_splice_read(struct file *filp, loff_t *ppos,
  61                                                                            struct pipe_inode_info *pipe, size_t len,
  62                                                                            unsigned int flags);
  63
  64 /* File operations structure */
  65 const struct file_operations swap_device_fops = {
  66         .owner = THIS_MODULE,
  67         .read = swap_device_read,
  68         .open = swap_device_open,
  69         .release = swap_device_release,
  70         .unlocked_ioctl = swap_device_ioctl,
  71         .splice_read = swap_device_splice_read,
  72 };
  73
  74 /* Typedefs for splice_* funcs. Prototypes are for linux-3.8.6 */
  75 typedef ssize_t(*splice_to_pipe_p_t)(struct pipe_inode_info *pipe,
  76                                          struct splice_pipe_desc *spd);
  77 typedef int(*splice_grow_spd_p_t)(const struct pipe_inode_info *pipe,
  78                                         struct splice_pipe_desc *spd);
  79
  80 static splice_to_pipe_p_t splice_to_pipe_p = NULL;
  81 static splice_grow_spd_p_t splice_grow_spd_p = NULL;
  82
  83 static msg_handler_t msg_handler = NULL;
  84
  85 /* Device numbers */
  86 static dev_t swap_device_no = 0;
  87
  88 /* Device cdev struct */
  89 static struct cdev *swap_device_cdev = NULL;
  90
  91 /* Device class struct */
  92 static struct class *swap_device_class = NULL;
  93
  94 /* Device device struct */
  95 static struct device *swap_device_device = NULL;
  96
  97 /* Reading tasks queue */
  98 static DECLARE_WAIT_QUEUE_HEAD(swap_device_wait);
  99
 100
 101 static atomic_t flag_wake_up = ATOMIC_INIT(0);
 102
 103 static void __bottom_wake_up(void)
 104 {
 105         if (waitqueue_active(&swap_device_wait))
 106                 wake_up_interruptible(&swap_device_wait);
 107 }
 108
 109 static void bottom_wake_up(struct work_struct *work)
 110 {
 111         if (atomic_read(&flag_wake_up)) {
 112                 atomic_set(&flag_wake_up, 0);
 113                 __bottom_wake_up();
 114         }
 115 }
 116
 117 static DECLARE_WORK(w_wake_up, bottom_wake_up);
 118
 119 static void exit_w_wake_up(void)
 120 {
 121         flush_scheduled_work();
 122         __bottom_wake_up();
 123 }
 124
 125
 126 /* We need this realization of splice_shrink_spd() because of the its desing
 127  * frequent changes that I have encountered in custom kernels */
 128 void swap_device_splice_shrink_spd(struct pipe_inode_info *pipe,
 129                                    struct splice_pipe_desc *spd)
 130 {
 131         if (pipe->buffers <= PIPE_DEF_BUFFERS)
 132                 return;
 133
 134         kfree(spd->pages);
 135         kfree(spd->partial);
 136 }
 137
 138
 139 /* Register device TODO Think of permanent major */
 140 int swap_device_init(void)
 141 {
 142         int result;
 143
 144         /* Allocating device major and minor nums for swap_device */
 145         result = alloc_chrdev_region(&swap_device_no, 0, 1, SWAP_DEVICE_NAME);
 146         if (result < 0) {
 147                 print_crit("Major number allocation has failed\n");
 148                 result = -E_SD_ALLOC_CHRDEV_FAIL;
 149                 goto init_fail;
 150         }
 151
 152         /* Creating device class. Using IS_ERR, because class_create returns ERR_PTR
 153          * on error. */
 154         swap_device_class = class_create(THIS_MODULE, SWAP_DEVICE_NAME);
 155         if (IS_ERR(swap_device_class)) {
 156                 print_crit("Class creation has failed\n");
 157                 result = -E_SD_CLASS_CREATE_FAIL;
 158                 goto init_fail;
 159         }
 160
 161         /* Cdev allocation */
 162         swap_device_cdev = cdev_alloc();
 163         if (!swap_device_cdev) {
 164                 print_crit("Cdev structure allocation has failed\n");
 165                 result = -E_SD_CDEV_ALLOC_FAIL;
 166                 goto init_fail;
 167         }
 168
 169         /* Cdev intialization and setting file operations */
 170         cdev_init(swap_device_cdev, &swap_device_fops);
 171
 172         /* Adding cdev to system */
 173         result = cdev_add(swap_device_cdev, swap_device_no, 1);
 174         if (result < 0) {
 175                 print_crit("Device adding has failed\n");
 176                 result = -E_SD_CDEV_ADD_FAIL;
 177                 goto init_fail;
 178         }
 179
 180         /* Create device struct */
 181         swap_device_device = device_create(swap_device_class, NULL, swap_device_no,
 182                                                                            "%s", SWAP_DEVICE_NAME);
 183         if (IS_ERR(swap_device_device)) {
 184                 print_crit("Device struct creating has failed\n");
 185                 result = -E_SD_DEVICE_CREATE_FAIL;
 186                 goto init_fail;
 187         }
 188
 189         /* Find splice_* funcs addresses */
 190         splice_to_pipe_p = (splice_to_pipe_p_t)swap_ksyms("splice_to_pipe");
 191         if (!splice_to_pipe_p) {
 192                 print_err("splice_to_pipe() not found!\n");
 193                 result = -E_SD_NO_SPLICE_FUNCS;
 194                 goto init_fail;
 195         }
 196
 197         splice_grow_spd_p = (splice_grow_spd_p_t)swap_ksyms("splice_grow_spd");
 198         if (!splice_grow_spd_p) {
 199                 print_err("splice_grow_spd() not found!\n");
 200                 result = -E_SD_NO_SPLICE_FUNCS;
 201                 goto init_fail;
 202         }
 203
 204         return 0;
 205
 206 init_fail:
 207         if (swap_device_cdev) {
 208                 cdev_del(swap_device_cdev);
 209         }
 210         if (swap_device_class) {
 211                 class_destroy(swap_device_class);
 212         }
 213         if (swap_device_no) {
 214                 unregister_chrdev_region(swap_device_no, 1);
 215         }
 216         return result;
 217 }
 218
 219 /* Unregister device TODO Check wether driver is registered */
 220 void swap_device_exit(void)
 221 {
 222         exit_w_wake_up();
 223
 224         splice_to_pipe_p = NULL;
 225         splice_grow_spd_p = NULL;
 226
 227         device_destroy(swap_device_class, swap_device_no);
 228         cdev_del(swap_device_cdev);
 229         class_destroy(swap_device_class);
 230         unregister_chrdev_region(swap_device_no, 1);
 231 }
 232
 233 static int swap_device_open(struct inode *inode, struct file *filp)
 234 {
 235         // TODO MOD_INC_USE_COUNT
 236         return 0;
 237 }
 238
 239 static int swap_device_release(struct inode *inode, struct file *filp)
 240 {
 241         // TODO MOD_DEC_USE_COUNT
 242         return 0;
 243 }
 244
 245 static ssize_t swap_device_read(struct file *filp, char __user *buf,
 246                                                                 size_t count, loff_t *f_pos)
 247 {
 248         /* Wait queue item that consists current task. It is used to be added in
 249          * swap_device_wait queue if there is no data to be read. */
 250         DEFINE_WAIT(wait);
 251         int result;
 252
 253         //TODO : Think about spin_locks to prevent reading race condition.
 254         while((result = driver_to_buffer_next_buffer_to_read()) != E_SD_SUCCESS) {
 255
 256                 /* Add process to the swap_device_wait queue and set the current task
 257                  * state TASK_INTERRUPTIBLE. If there is any data to be read, then the
 258                  * current task is removed from the swap_device_wait queue and its state
 259                  * is changed to this. */
 260                 prepare_to_wait(&swap_device_wait, &wait, TASK_INTERRUPTIBLE);
 261
 262                 if (result < 0) {
 263                         result = 0;
 264                         goto swap_device_read_error;
 265                 } else if (result == E_SD_NO_DATA_TO_READ) {
 266                         /* Yes, E_SD_NO_DATA_TO_READ should be positive, cause it's not
 267                          * really an error */
 268                         if (filp->f_flags & O_NONBLOCK) {
 269                                 result = -EAGAIN;
 270                                 goto swap_device_read_error;
 271                         }
 272                         if (signal_pending(current)) {
 273                                 result = -ERESTARTSYS;
 274                                 goto swap_device_read_error;
 275                         }
 276                         schedule();
 277                         finish_wait(&swap_device_wait, &wait);
 278                 }
 279         }
 280
 281         result = driver_to_buffer_read(buf, count);
 282         /* If there is an error - return 0 */
 283         if (result < 0)
 284                 result = 0;
 285
 286
 287         return result;
 288
 289 swap_device_read_error:
 290         finish_wait(&swap_device_wait, &wait);
 291
 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                         break;
 327                 }
 328                 case SWAP_DRIVER_NEXT_BUFFER_TO_READ:
 329                 {
 330                         /* Use this carefully */
 331                         result = driver_to_buffer_next_buffer_to_read();
 332                         if (result == E_SD_NO_DATA_TO_READ) {
 333                                 /* TODO Do what we usually do when there are no subbuffers to
 334                                  * read (make daemon sleep ?) */
 335                         }
 336                         break;
 337                 }
 338                 case SWAP_DRIVER_FLUSH_BUFFER:
 339                 {
 340                         result = driver_to_buffer_flush();
 341                         break;
 342                 }
 343                 case SWAP_DRIVER_MSG:
 344                 {
 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                 }
 353                 case SWAP_DRIVER_WAKE_UP:
 354                 {
 355                         swap_device_wake_up_process();
 356                         result = E_SD_SUCCESS;
 357                         break;
 358                 }
 359                 default:
 360                         print_warn("Unknown command %d\n", cmd);
 361                         result = -EINVAL;
 362                         break;
 363
 364         }
 365         return result;
 366 }
 367
 368 static void swap_device_pipe_buf_release(struct pipe_inode_info *inode,
 369                                                                                  struct pipe_buffer *pipe)
 370 {
 371         __free_page(pipe->page);
 372 }
 373
 374 static void swap_device_page_release(struct splice_pipe_desc *spd,
 375                                                                          unsigned int i)
 376 {
 377         __free_page(spd->pages[i]);
 378 }
 379
 380 static const struct pipe_buf_operations swap_device_pipe_buf_ops = {
 381         .can_merge = 0,
 382         .map = generic_pipe_buf_map,
 383         .unmap = generic_pipe_buf_unmap,
 384         .confirm = generic_pipe_buf_confirm,
 385         .release = swap_device_pipe_buf_release,
 386         .steal = generic_pipe_buf_steal,
 387         .get = generic_pipe_buf_get
 388 };
 389
 390 static ssize_t swap_device_splice_read(struct file *filp, loff_t *ppos,
 391                                                                            struct pipe_inode_info *pipe,
 392                                                                            size_t len, unsigned int flags)
 393 {
 394         /* Wait queue item that consists current task. It is used to be added in
 395          * swap_device_wait queue if there is no data to be read. */
 396         DEFINE_WAIT(wait);
 397
 398         int result;
 399         struct page *pages[PIPE_DEF_BUFFERS];
 400         struct partial_page partial[PIPE_DEF_BUFFERS];
 401         struct splice_pipe_desc spd = {
 402                 .pages = pages,
 403                 .partial = partial,
 404 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 4, 5))
 405                 .nr_pages_max = PIPE_DEF_BUFFERS,
 406 #endif
 407                 .nr_pages = 0,
 408                 .flags = flags,
 409                 .ops = &swap_device_pipe_buf_ops,
 410                 .spd_release = swap_device_page_release,
 411         };
 412
 413         /* Get next buffer to read */
 414         //TODO : Think about spin_locks to prevent reading race condition.
 415         while((result = driver_to_buffer_next_buffer_to_read()) != E_SD_SUCCESS) {
 416
 417                 /* Add process to the swap_device_wait queue and set the current task
 418                  * state TASK_INTERRUPTIBLE. If there is any data to be read, then the
 419                  * current task is removed from the swap_device_wait queue and its state
 420                  * is changed. */
 421                 prepare_to_wait(&swap_device_wait, &wait, TASK_INTERRUPTIBLE);
 422                 if (result < 0) {
 423                         print_err("driver_to_buffer_next_buffer_to_read error %d\n", result);
 424                         //TODO Error return to OS
 425                         result = 0;
 426                         goto swap_device_splice_read_error;
 427                 } else if (result == E_SD_NO_DATA_TO_READ) {
 428                         if (filp->f_flags & O_NONBLOCK) {
 429                                 result = -EAGAIN;
 430                                 goto swap_device_splice_read_error;
 431                         }
 432                         if (signal_pending(current)) {
 433                                 result = -ERESTARTSYS;
 434                                 goto swap_device_splice_read_error;
 435                         }
 436                         schedule();
 437                         finish_wait(&swap_device_wait, &wait);
 438                 }
 439         }
 440
 441         if (splice_grow_spd_p(pipe, &spd)) {
 442                 result = -ENOMEM;
 443                 goto swap_device_splice_read_out;
 444         }
 445
 446         result = driver_to_buffer_fill_spd(&spd);
 447         if (result != 0) {
 448                 print_err("Cannot fill spd for splice\n");
 449                 goto swap_device_shrink_spd;
 450         }
 451
 452         result = splice_to_pipe_p(pipe, &spd);
 453
 454 swap_device_shrink_spd:
 455         swap_device_splice_shrink_spd(pipe, &spd);
 456
 457 swap_device_splice_read_out:
 458         return result;
 459
 460 swap_device_splice_read_error:
 461         finish_wait(&swap_device_wait, &wait);
 462
 463         return result;
 464 }
 465
 466 void swap_device_wake_up_process(void)
 467 {
 468         if (atomic_read(&flag_wake_up) == 0) {
 469                 atomic_set(&flag_wake_up, 1);
 470                 schedule_work(&w_wake_up);
 471         }
 472 }
 473
 474 void set_msg_handler(msg_handler_t mh)
 475 {
 476         msg_handler = mh;
 477 }
 478 EXPORT_SYMBOL_GPL(set_msg_handler);