drivers/misc/lkdtm.c

   1 /*
   2  * Kprobe module for testing crash dumps
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2006
  19  *
  20  * Author: Ankita Garg <ankita@in.ibm.com>
  21  *
  22  * This module induces system failures at predefined crashpoints to
  23  * evaluate the reliability of crash dumps obtained using different dumping
  24  * solutions.
  25  *
  26  * It is adapted from the Linux Kernel Dump Test Tool by
  27  * Fernando Luis Vazquez Cao <http://lkdtt.sourceforge.net>
  28  *
  29  * Debugfs support added by Simon Kagstrom <simon.kagstrom@netinsight.net>
  30  *
  31  * See Documentation/fault-injection/provoke-crashes.txt for instructions
  32  */
  33
  34 #include <linux/kernel.h>
  35 #include <linux/fs.h>
  36 #include <linux/module.h>
  37 #include <linux/buffer_head.h>
  38 #include <linux/kprobes.h>
  39 #include <linux/list.h>
  40 #include <linux/init.h>
  41 #include <linux/interrupt.h>
  42 #include <linux/hrtimer.h>
  43 #include <linux/slab.h>
  44 #include <scsi/scsi_cmnd.h>
  45 #include <linux/debugfs.h>
  46
  47 #ifdef CONFIG_IDE
  48 #include <linux/ide.h>
  49 #endif
  50
  51 #define DEFAULT_COUNT 10
  52 #define REC_NUM_DEFAULT 10
  53
  54 enum cname {
  55         CN_INVALID,
  56         CN_INT_HARDWARE_ENTRY,
  57         CN_INT_HW_IRQ_EN,
  58         CN_INT_TASKLET_ENTRY,
  59         CN_FS_DEVRW,
  60         CN_MEM_SWAPOUT,
  61         CN_TIMERADD,
  62         CN_SCSI_DISPATCH_CMD,
  63         CN_IDE_CORE_CP,
  64         CN_DIRECT,
  65 };
  66
  67 enum ctype {
  68         CT_NONE,
  69         CT_PANIC,
  70         CT_BUG,
  71         CT_EXCEPTION,
  72         CT_LOOP,
  73         CT_OVERFLOW,
  74         CT_CORRUPT_STACK,
  75         CT_UNALIGNED_LOAD_STORE_WRITE,
  76         CT_OVERWRITE_ALLOCATION,
  77         CT_WRITE_AFTER_FREE,
  78         CT_SOFTLOCKUP,
  79         CT_HARDLOCKUP,
  80         CT_HUNG_TASK,
  81 };
  82
  83 static char* cp_name[] = {
  84         "INT_HARDWARE_ENTRY",
  85         "INT_HW_IRQ_EN",
  86         "INT_TASKLET_ENTRY",
  87         "FS_DEVRW",
  88         "MEM_SWAPOUT",
  89         "TIMERADD",
  90         "SCSI_DISPATCH_CMD",
  91         "IDE_CORE_CP",
  92         "DIRECT",
  93 };
  94
  95 static char* cp_type[] = {
  96         "PANIC",
  97         "BUG",
  98         "EXCEPTION",
  99         "LOOP",
 100         "OVERFLOW",
 101         "CORRUPT_STACK",
 102         "UNALIGNED_LOAD_STORE_WRITE",
 103         "OVERWRITE_ALLOCATION",
 104         "WRITE_AFTER_FREE",
 105         "SOFTLOCKUP",
 106         "HARDLOCKUP",
 107         "HUNG_TASK",
 108 };
 109
 110 static struct jprobe lkdtm;
 111
 112 static int lkdtm_parse_commandline(void);
 113 static void lkdtm_handler(void);
 114
 115 static char* cpoint_name;
 116 static char* cpoint_type;
 117 static int cpoint_count = DEFAULT_COUNT;
 118 static int recur_count = REC_NUM_DEFAULT;
 119
 120 static enum cname cpoint = CN_INVALID;
 121 static enum ctype cptype = CT_NONE;
 122 static int count = DEFAULT_COUNT;
 123 static DEFINE_SPINLOCK(count_lock);
 124
 125 module_param(recur_count, int, 0644);
 126 MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test, "\
 127                                  "default is 10");
 128 module_param(cpoint_name, charp, 0444);
 129 MODULE_PARM_DESC(cpoint_name, " Crash Point, where kernel is to be crashed");
 130 module_param(cpoint_type, charp, 0444);
 131 MODULE_PARM_DESC(cpoint_type, " Crash Point Type, action to be taken on "\
 132                                 "hitting the crash point");
 133 module_param(cpoint_count, int, 0644);
 134 MODULE_PARM_DESC(cpoint_count, " Crash Point Count, number of times the "\
 135                                 "crash point is to be hit to trigger action");
 136
 137 static unsigned int jp_do_irq(unsigned int irq)
 138 {
 139         lkdtm_handler();
 140         jprobe_return();
 141         return 0;
 142 }
 143
 144 static irqreturn_t jp_handle_irq_event(unsigned int irq,
 145                                        struct irqaction *action)
 146 {
 147         lkdtm_handler();
 148         jprobe_return();
 149         return 0;
 150 }
 151
 152 static void jp_tasklet_action(struct softirq_action *a)
 153 {
 154         lkdtm_handler();
 155         jprobe_return();
 156 }
 157
 158 static void jp_ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
 159 {
 160         lkdtm_handler();
 161         jprobe_return();
 162 }
 163
 164 struct scan_control;
 165
 166 static unsigned long jp_shrink_inactive_list(unsigned long max_scan,
 167                                              struct zone *zone,
 168                                              struct scan_control *sc)
 169 {
 170         lkdtm_handler();
 171         jprobe_return();
 172         return 0;
 173 }
 174
 175 static int jp_hrtimer_start(struct hrtimer *timer, ktime_t tim,
 176                             const enum hrtimer_mode mode)
 177 {
 178         lkdtm_handler();
 179         jprobe_return();
 180         return 0;
 181 }
 182
 183 static int jp_scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 184 {
 185         lkdtm_handler();
 186         jprobe_return();
 187         return 0;
 188 }
 189
 190 #ifdef CONFIG_IDE
 191 int jp_generic_ide_ioctl(ide_drive_t *drive, struct file *file,
 192                         struct block_device *bdev, unsigned int cmd,
 193                         unsigned long arg)
 194 {
 195         lkdtm_handler();
 196         jprobe_return();
 197         return 0;
 198 }
 199 #endif
 200
 201 /* Return the crashpoint number or NONE if the name is invalid */
 202 static enum ctype parse_cp_type(const char *what, size_t count)
 203 {
 204         int i;
 205
 206         for (i = 0; i < ARRAY_SIZE(cp_type); i++) {
 207                 if (!strcmp(what, cp_type[i]))
 208                         return i + 1;
 209         }
 210
 211         return CT_NONE;
 212 }
 213
 214 static const char *cp_type_to_str(enum ctype type)
 215 {
 216         if (type == CT_NONE || type < 0 || type > ARRAY_SIZE(cp_type))
 217                 return "None";
 218
 219         return cp_type[type - 1];
 220 }
 221
 222 static const char *cp_name_to_str(enum cname name)
 223 {
 224         if (name == CN_INVALID || name < 0 || name > ARRAY_SIZE(cp_name))
 225                 return "INVALID";
 226
 227         return cp_name[name - 1];
 228 }
 229
 230
 231 static int lkdtm_parse_commandline(void)
 232 {
 233         int i;
 234         unsigned long flags;
 235
 236         if (cpoint_count < 1 || recur_count < 1)
 237                 return -EINVAL;
 238
 239         spin_lock_irqsave(&count_lock, flags);
 240         count = cpoint_count;
 241         spin_unlock_irqrestore(&count_lock, flags);
 242
 243         /* No special parameters */
 244         if (!cpoint_type && !cpoint_name)
 245                 return 0;
 246
 247         /* Neither or both of these need to be set */
 248         if (!cpoint_type || !cpoint_name)
 249                 return -EINVAL;
 250
 251         cptype = parse_cp_type(cpoint_type, strlen(cpoint_type));
 252         if (cptype == CT_NONE)
 253                 return -EINVAL;
 254
 255         for (i = 0; i < ARRAY_SIZE(cp_name); i++) {
 256                 if (!strcmp(cpoint_name, cp_name[i])) {
 257                         cpoint = i + 1;
 258                         return 0;
 259                 }
 260         }
 261
 262         /* Could not find a valid crash point */
 263         return -EINVAL;
 264 }
 265
 266 static int recursive_loop(int a)
 267 {
 268         char buf[1024];
 269
 270         memset(buf,0xFF,1024);
 271         recur_count--;
 272         if (!recur_count)
 273                 return 0;
 274         else
 275                 return recursive_loop(a);
 276 }
 277
 278 static void lkdtm_do_action(enum ctype which)
 279 {
 280         switch (which) {
 281         case CT_PANIC:
 282                 panic("dumptest");
 283                 break;
 284         case CT_BUG:
 285                 BUG();
 286                 break;
 287         case CT_EXCEPTION:
 288                 *((int *) 0) = 0;
 289                 break;
 290         case CT_LOOP:
 291                 for (;;)
 292                         ;
 293                 break;
 294         case CT_OVERFLOW:
 295                 (void) recursive_loop(0);
 296                 break;
 297         case CT_CORRUPT_STACK: {
 298                 volatile u32 data[8];
 299                 volatile u32 *p = data;
 300
 301                 p[12] = 0x12345678;
 302                 break;
 303         }
 304         case CT_UNALIGNED_LOAD_STORE_WRITE: {
 305                 static u8 data[5] __attribute__((aligned(4))) = {1, 2,
 306                                 3, 4, 5};
 307                 u32 *p;
 308                 u32 val = 0x12345678;
 309
 310                 p = (u32 *)(data + 1);
 311                 if (*p == 0)
 312                         val = 0x87654321;
 313                 *p = val;
 314                  break;
 315         }
 316         case CT_OVERWRITE_ALLOCATION: {
 317                 size_t len = 1020;
 318                 u32 *data = kmalloc(len, GFP_KERNEL);
 319
 320                 data[1024 / sizeof(u32)] = 0x12345678;
 321                 kfree(data);
 322                 break;
 323         }
 324         case CT_WRITE_AFTER_FREE: {
 325                 size_t len = 1024;
 326                 u32 *data = kmalloc(len, GFP_KERNEL);
 327
 328                 kfree(data);
 329                 schedule();
 330                 memset(data, 0x78, len);
 331                 break;
 332         }
 333         case CT_SOFTLOCKUP:
 334                 preempt_disable();
 335                 for (;;)
 336                         cpu_relax();
 337                 break;
 338         case CT_HARDLOCKUP:
 339                 local_irq_disable();
 340                 for (;;)
 341                         cpu_relax();
 342                 break;
 343         case CT_HUNG_TASK:
 344                 set_current_state(TASK_UNINTERRUPTIBLE);
 345                 schedule();
 346                 break;
 347         case CT_NONE:
 348         default:
 349                 break;
 350         }
 351
 352 }
 353
 354 static void lkdtm_handler(void)
 355 {
 356         unsigned long flags;
 357
 358         spin_lock_irqsave(&count_lock, flags);
 359         count--;
 360         printk(KERN_INFO "lkdtm: Crash point %s of type %s hit, trigger in %d rounds\n",
 361                         cp_name_to_str(cpoint), cp_type_to_str(cptype), count);
 362
 363         if (count == 0) {
 364                 lkdtm_do_action(cptype);
 365                 count = cpoint_count;
 366         }
 367         spin_unlock_irqrestore(&count_lock, flags);
 368 }
 369
 370 static int lkdtm_register_cpoint(enum cname which)
 371 {
 372         int ret;
 373
 374         cpoint = CN_INVALID;
 375         if (lkdtm.entry != NULL)
 376                 unregister_jprobe(&lkdtm);
 377
 378         switch (which) {
 379         case CN_DIRECT:
 380                 lkdtm_do_action(cptype);
 381                 return 0;
 382         case CN_INT_HARDWARE_ENTRY:
 383                 lkdtm.kp.symbol_name = "do_IRQ";
 384                 lkdtm.entry = (kprobe_opcode_t*) jp_do_irq;
 385                 break;
 386         case CN_INT_HW_IRQ_EN:
 387                 lkdtm.kp.symbol_name = "handle_IRQ_event";
 388                 lkdtm.entry = (kprobe_opcode_t*) jp_handle_irq_event;
 389                 break;
 390         case CN_INT_TASKLET_ENTRY:
 391                 lkdtm.kp.symbol_name = "tasklet_action";
 392                 lkdtm.entry = (kprobe_opcode_t*) jp_tasklet_action;
 393                 break;
 394         case CN_FS_DEVRW:
 395                 lkdtm.kp.symbol_name = "ll_rw_block";
 396                 lkdtm.entry = (kprobe_opcode_t*) jp_ll_rw_block;
 397                 break;
 398         case CN_MEM_SWAPOUT:
 399                 lkdtm.kp.symbol_name = "shrink_inactive_list";
 400                 lkdtm.entry = (kprobe_opcode_t*) jp_shrink_inactive_list;
 401                 break;
 402         case CN_TIMERADD:
 403                 lkdtm.kp.symbol_name = "hrtimer_start";
 404                 lkdtm.entry = (kprobe_opcode_t*) jp_hrtimer_start;
 405                 break;
 406         case CN_SCSI_DISPATCH_CMD:
 407                 lkdtm.kp.symbol_name = "scsi_dispatch_cmd";
 408                 lkdtm.entry = (kprobe_opcode_t*) jp_scsi_dispatch_cmd;
 409                 break;
 410         case CN_IDE_CORE_CP:
 411 #ifdef CONFIG_IDE
 412                 lkdtm.kp.symbol_name = "generic_ide_ioctl";
 413                 lkdtm.entry = (kprobe_opcode_t*) jp_generic_ide_ioctl;
 414 #else
 415                 printk(KERN_INFO "lkdtm: Crash point not available\n");
 416                 return -EINVAL;
 417 #endif
 418                 break;
 419         default:
 420                 printk(KERN_INFO "lkdtm: Invalid Crash Point\n");
 421                 return -EINVAL;
 422         }
 423
 424         cpoint = which;
 425         if ((ret = register_jprobe(&lkdtm)) < 0) {
 426                 printk(KERN_INFO "lkdtm: Couldn't register jprobe\n");
 427                 cpoint = CN_INVALID;
 428         }
 429
 430         return ret;
 431 }
 432
 433 static ssize_t do_register_entry(enum cname which, struct file *f,
 434                 const char __user *user_buf, size_t count, loff_t *off)
 435 {
 436         char *buf;
 437         int err;
 438
 439         if (count >= PAGE_SIZE)
 440                 return -EINVAL;
 441
 442         buf = (char *)__get_free_page(GFP_KERNEL);
 443         if (!buf)
 444                 return -ENOMEM;
 445         if (copy_from_user(buf, user_buf, count)) {
 446                 free_page((unsigned long) buf);
 447                 return -EFAULT;
 448         }
 449         /* NULL-terminate and remove enter */
 450         buf[count] = '\0';
 451         strim(buf);
 452
 453         cptype = parse_cp_type(buf, count);
 454         free_page((unsigned long) buf);
 455
 456         if (cptype == CT_NONE)
 457                 return -EINVAL;
 458
 459         err = lkdtm_register_cpoint(which);
 460         if (err < 0)
 461                 return err;
 462
 463         *off += count;
 464
 465         return count;
 466 }
 467
 468 /* Generic read callback that just prints out the available crash types */
 469 static ssize_t lkdtm_debugfs_read(struct file *f, char __user *user_buf,
 470                 size_t count, loff_t *off)
 471 {
 472         char *buf;
 473         int i, n, out;
 474
 475         buf = (char *)__get_free_page(GFP_KERNEL);
 476
 477         n = snprintf(buf, PAGE_SIZE, "Available crash types:\n");
 478         for (i = 0; i < ARRAY_SIZE(cp_type); i++)
 479                 n += snprintf(buf + n, PAGE_SIZE - n, "%s\n", cp_type[i]);
 480         buf[n] = '\0';
 481
 482         out = simple_read_from_buffer(user_buf, count, off,
 483                                       buf, n);
 484         free_page((unsigned long) buf);
 485
 486         return out;
 487 }
 488
 489 static int lkdtm_debugfs_open(struct inode *inode, struct file *file)
 490 {
 491         return 0;
 492 }
 493
 494
 495 static ssize_t int_hardware_entry(struct file *f, const char __user *buf,
 496                 size_t count, loff_t *off)
 497 {
 498         return do_register_entry(CN_INT_HARDWARE_ENTRY, f, buf, count, off);
 499 }
 500
 501 static ssize_t int_hw_irq_en(struct file *f, const char __user *buf,
 502                 size_t count, loff_t *off)
 503 {
 504         return do_register_entry(CN_INT_HW_IRQ_EN, f, buf, count, off);
 505 }
 506
 507 static ssize_t int_tasklet_entry(struct file *f, const char __user *buf,
 508                 size_t count, loff_t *off)
 509 {
 510         return do_register_entry(CN_INT_TASKLET_ENTRY, f, buf, count, off);
 511 }
 512
 513 static ssize_t fs_devrw_entry(struct file *f, const char __user *buf,
 514                 size_t count, loff_t *off)
 515 {
 516         return do_register_entry(CN_FS_DEVRW, f, buf, count, off);
 517 }
 518
 519 static ssize_t mem_swapout_entry(struct file *f, const char __user *buf,
 520                 size_t count, loff_t *off)
 521 {
 522         return do_register_entry(CN_MEM_SWAPOUT, f, buf, count, off);
 523 }
 524
 525 static ssize_t timeradd_entry(struct file *f, const char __user *buf,
 526                 size_t count, loff_t *off)
 527 {
 528         return do_register_entry(CN_TIMERADD, f, buf, count, off);
 529 }
 530
 531 static ssize_t scsi_dispatch_cmd_entry(struct file *f,
 532                 const char __user *buf, size_t count, loff_t *off)
 533 {
 534         return do_register_entry(CN_SCSI_DISPATCH_CMD, f, buf, count, off);
 535 }
 536
 537 static ssize_t ide_core_cp_entry(struct file *f, const char __user *buf,
 538                 size_t count, loff_t *off)
 539 {
 540         return do_register_entry(CN_IDE_CORE_CP, f, buf, count, off);
 541 }
 542
 543 /* Special entry to just crash directly. Available without KPROBEs */
 544 static ssize_t direct_entry(struct file *f, const char __user *user_buf,
 545                 size_t count, loff_t *off)
 546 {
 547         enum ctype type;
 548         char *buf;
 549
 550         if (count >= PAGE_SIZE)
 551                 return -EINVAL;
 552         if (count < 1)
 553                 return -EINVAL;
 554
 555         buf = (char *)__get_free_page(GFP_KERNEL);
 556         if (!buf)
 557                 return -ENOMEM;
 558         if (copy_from_user(buf, user_buf, count)) {
 559                 free_page((unsigned long) buf);
 560                 return -EFAULT;
 561         }
 562         /* NULL-terminate and remove enter */
 563         buf[count] = '\0';
 564         strim(buf);
 565
 566         type = parse_cp_type(buf, count);
 567         free_page((unsigned long) buf);
 568         if (type == CT_NONE)
 569                 return -EINVAL;
 570
 571         printk(KERN_INFO "lkdtm: Performing direct entry %s\n",
 572                         cp_type_to_str(type));
 573         lkdtm_do_action(type);
 574         *off += count;
 575
 576         return count;
 577 }
 578
 579 struct crash_entry {
 580         const char *name;
 581         const struct file_operations fops;
 582 };
 583
 584 static const struct crash_entry crash_entries[] = {
 585         {"DIRECT", {.read = lkdtm_debugfs_read,
 586                         .llseek = generic_file_llseek,
 587                         .open = lkdtm_debugfs_open,
 588                         .write = direct_entry} },
 589         {"INT_HARDWARE_ENTRY", {.read = lkdtm_debugfs_read,
 590                         .llseek = generic_file_llseek,
 591                         .open = lkdtm_debugfs_open,
 592                         .write = int_hardware_entry} },
 593         {"INT_HW_IRQ_EN", {.read = lkdtm_debugfs_read,
 594                         .llseek = generic_file_llseek,
 595                         .open = lkdtm_debugfs_open,
 596                         .write = int_hw_irq_en} },
 597         {"INT_TASKLET_ENTRY", {.read = lkdtm_debugfs_read,
 598                         .llseek = generic_file_llseek,
 599                         .open = lkdtm_debugfs_open,
 600                         .write = int_tasklet_entry} },
 601         {"FS_DEVRW", {.read = lkdtm_debugfs_read,
 602                         .llseek = generic_file_llseek,
 603                         .open = lkdtm_debugfs_open,
 604                         .write = fs_devrw_entry} },
 605         {"MEM_SWAPOUT", {.read = lkdtm_debugfs_read,
 606                         .llseek = generic_file_llseek,
 607                         .open = lkdtm_debugfs_open,
 608                         .write = mem_swapout_entry} },
 609         {"TIMERADD", {.read = lkdtm_debugfs_read,
 610                         .llseek = generic_file_llseek,
 611                         .open = lkdtm_debugfs_open,
 612                         .write = timeradd_entry} },
 613         {"SCSI_DISPATCH_CMD", {.read = lkdtm_debugfs_read,
 614                         .llseek = generic_file_llseek,
 615                         .open = lkdtm_debugfs_open,
 616                         .write = scsi_dispatch_cmd_entry} },
 617         {"IDE_CORE_CP", {.read = lkdtm_debugfs_read,
 618                         .llseek = generic_file_llseek,
 619                         .open = lkdtm_debugfs_open,
 620                         .write = ide_core_cp_entry} },
 621 };
 622
 623 static struct dentry *lkdtm_debugfs_root;
 624
 625 static int __init lkdtm_module_init(void)
 626 {
 627         int ret = -EINVAL;
 628         int n_debugfs_entries = 1; /* Assume only the direct entry */
 629         int i;
 630
 631         /* Register debugfs interface */
 632         lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);
 633         if (!lkdtm_debugfs_root) {
 634                 printk(KERN_ERR "lkdtm: creating root dir failed\n");
 635                 return -ENODEV;
 636         }
 637
 638 #ifdef CONFIG_KPROBES
 639         n_debugfs_entries = ARRAY_SIZE(crash_entries);
 640 #endif
 641
 642         for (i = 0; i < n_debugfs_entries; i++) {
 643                 const struct crash_entry *cur = &crash_entries[i];
 644                 struct dentry *de;
 645
 646                 de = debugfs_create_file(cur->name, 0644, lkdtm_debugfs_root,
 647                                 NULL, &cur->fops);
 648                 if (de == NULL) {
 649                         printk(KERN_ERR "lkdtm: could not create %s\n",
 650                                         cur->name);
 651                         goto out_err;
 652                 }
 653         }
 654
 655         if (lkdtm_parse_commandline() == -EINVAL) {
 656                 printk(KERN_INFO "lkdtm: Invalid command\n");
 657                 goto out_err;
 658         }
 659
 660         if (cpoint != CN_INVALID && cptype != CT_NONE) {
 661                 ret = lkdtm_register_cpoint(cpoint);
 662                 if (ret < 0) {
 663                         printk(KERN_INFO "lkdtm: Invalid crash point %d\n",
 664                                         cpoint);
 665                         goto out_err;
 666                 }
 667                 printk(KERN_INFO "lkdtm: Crash point %s of type %s registered\n",
 668                                 cpoint_name, cpoint_type);
 669         } else {
 670                 printk(KERN_INFO "lkdtm: No crash points registered, enable through debugfs\n");
 671         }
 672
 673         return 0;
 674
 675 out_err:
 676         debugfs_remove_recursive(lkdtm_debugfs_root);
 677         return ret;
 678 }
 679
 680 static void __exit lkdtm_module_exit(void)
 681 {
 682         debugfs_remove_recursive(lkdtm_debugfs_root);
 683
 684         unregister_jprobe(&lkdtm);
 685         printk(KERN_INFO "lkdtm: Crash point unregistered\n");
 686 }
 687
 688 module_init(lkdtm_module_init);
 689 module_exit(lkdtm_module_exit);
 690
 691 MODULE_LICENSE("GPL");