lib/dynamic_debug.c

   1 /*
   2  * lib/dynamic_debug.c
   3  *
   4  * make pr_debug()/dev_dbg() calls runtime configurable based upon their
   5  * source module.
   6  *
   7  * Copyright (C) 2008 Jason Baron <jbaron@redhat.com>
   8  * By Greg Banks <gnb@melbourne.sgi.com>
   9  * Copyright (c) 2008 Silicon Graphics Inc.  All Rights Reserved.
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/moduleparam.h>
  15 #include <linux/kallsyms.h>
  16 #include <linux/version.h>
  17 #include <linux/types.h>
  18 #include <linux/mutex.h>
  19 #include <linux/proc_fs.h>
  20 #include <linux/seq_file.h>
  21 #include <linux/list.h>
  22 #include <linux/sysctl.h>
  23 #include <linux/ctype.h>
  24 #include <linux/string.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/dynamic_debug.h>
  27 #include <linux/debugfs.h>
  28 #include <linux/slab.h>
  29
  30 extern struct _ddebug __start___verbose[];
  31 extern struct _ddebug __stop___verbose[];
  32
  33 /* dynamic_debug_enabled, and dynamic_debug_enabled2 are bitmasks in which
  34  * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They
  35  * use independent hash functions, to reduce the chance of false positives.
  36  */
  37 long long dynamic_debug_enabled;
  38 EXPORT_SYMBOL_GPL(dynamic_debug_enabled);
  39 long long dynamic_debug_enabled2;
  40 EXPORT_SYMBOL_GPL(dynamic_debug_enabled2);
  41
  42 struct ddebug_table {
  43         struct list_head link;
  44         char *mod_name;
  45         unsigned int num_ddebugs;
  46         unsigned int num_enabled;
  47         struct _ddebug *ddebugs;
  48 };
  49
  50 struct ddebug_query {
  51         const char *filename;
  52         const char *module;
  53         const char *function;
  54         const char *format;
  55         unsigned int first_lineno, last_lineno;
  56 };
  57
  58 struct ddebug_iter {
  59         struct ddebug_table *table;
  60         unsigned int idx;
  61 };
  62
  63 static DEFINE_MUTEX(ddebug_lock);
  64 static LIST_HEAD(ddebug_tables);
  65 static int verbose = 0;
  66
  67 /* Return the last part of a pathname */
  68 static inline const char *basename(const char *path)
  69 {
  70         const char *tail = strrchr(path, '/');
  71         return tail ? tail+1 : path;
  72 }
  73
  74 /* format a string into buf[] which describes the _ddebug's flags */
  75 static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
  76                                     size_t maxlen)
  77 {
  78         char *p = buf;
  79
  80         BUG_ON(maxlen < 4);
  81         if (dp->flags & _DPRINTK_FLAGS_PRINT)
  82                 *p++ = 'p';
  83         if (p == buf)
  84                 *p++ = '-';
  85         *p = '\0';
  86
  87         return buf;
  88 }
  89
  90 /*
  91  * must be called with ddebug_lock held
  92  */
  93
  94 static int disabled_hash(char hash, bool first_table)
  95 {
  96         struct ddebug_table *dt;
  97         char table_hash_value;
  98
  99         list_for_each_entry(dt, &ddebug_tables, link) {
 100                 if (first_table)
 101                         table_hash_value = dt->ddebugs->primary_hash;
 102                 else
 103                         table_hash_value = dt->ddebugs->secondary_hash;
 104                 if (dt->num_enabled && (hash == table_hash_value))
 105                         return 0;
 106         }
 107         return 1;
 108 }
 109
 110 /*
 111  * Search the tables for _ddebug's which match the given
 112  * `query' and apply the `flags' and `mask' to them.  Tells
 113  * the user which ddebug's were changed, or whether none
 114  * were matched.
 115  */
 116 static void ddebug_change(const struct ddebug_query *query,
 117                            unsigned int flags, unsigned int mask)
 118 {
 119         int i;
 120         struct ddebug_table *dt;
 121         unsigned int newflags;
 122         unsigned int nfound = 0;
 123         char flagbuf[8];
 124
 125         /* search for matching ddebugs */
 126         mutex_lock(&ddebug_lock);
 127         list_for_each_entry(dt, &ddebug_tables, link) {
 128
 129                 /* match against the module name */
 130                 if (query->module != NULL &&
 131                     strcmp(query->module, dt->mod_name))
 132                         continue;
 133
 134                 for (i = 0 ; i < dt->num_ddebugs ; i++) {
 135                         struct _ddebug *dp = &dt->ddebugs[i];
 136
 137                         /* match against the source filename */
 138                         if (query->filename != NULL &&
 139                             strcmp(query->filename, dp->filename) &&
 140                             strcmp(query->filename, basename(dp->filename)))
 141                                 continue;
 142
 143                         /* match against the function */
 144                         if (query->function != NULL &&
 145                             strcmp(query->function, dp->function))
 146                                 continue;
 147
 148                         /* match against the format */
 149                         if (query->format != NULL &&
 150                             strstr(dp->format, query->format) == NULL)
 151                                 continue;
 152
 153                         /* match against the line number range */
 154                         if (query->first_lineno &&
 155                             dp->lineno < query->first_lineno)
 156                                 continue;
 157                         if (query->last_lineno &&
 158                             dp->lineno > query->last_lineno)
 159                                 continue;
 160
 161                         nfound++;
 162
 163                         newflags = (dp->flags & mask) | flags;
 164                         if (newflags == dp->flags)
 165                                 continue;
 166
 167                         if (!newflags)
 168                                 dt->num_enabled--;
 169                         else if (!dp->flags)
 170                                 dt->num_enabled++;
 171                         dp->flags = newflags;
 172                         if (newflags) {
 173                                 dynamic_debug_enabled |=
 174                                                 (1LL << dp->primary_hash);
 175                                 dynamic_debug_enabled2 |=
 176                                                 (1LL << dp->secondary_hash);
 177                         } else {
 178                                 if (disabled_hash(dp->primary_hash, true))
 179                                         dynamic_debug_enabled &=
 180                                                 ~(1LL << dp->primary_hash);
 181                                 if (disabled_hash(dp->secondary_hash, false))
 182                                         dynamic_debug_enabled2 &=
 183                                                 ~(1LL << dp->secondary_hash);
 184                         }
 185                         if (verbose)
 186                                 printk(KERN_INFO
 187                                         "ddebug: changed %s:%d [%s]%s %s\n",
 188                                         dp->filename, dp->lineno,
 189                                         dt->mod_name, dp->function,
 190                                         ddebug_describe_flags(dp, flagbuf,
 191                                                         sizeof(flagbuf)));
 192                 }
 193         }
 194         mutex_unlock(&ddebug_lock);
 195
 196         if (!nfound && verbose)
 197                 printk(KERN_INFO "ddebug: no matches for query\n");
 198 }
 199
 200 /*
 201  * Split the buffer `buf' into space-separated words.
 202  * Handles simple " and ' quoting, i.e. without nested,
 203  * embedded or escaped \".  Return the number of words
 204  * or <0 on error.
 205  */
 206 static int ddebug_tokenize(char *buf, char *words[], int maxwords)
 207 {
 208         int nwords = 0;
 209
 210         while (*buf) {
 211                 char *end;
 212
 213                 /* Skip leading whitespace */
 214                 buf = skip_spaces(buf);
 215                 if (!*buf)
 216                         break;  /* oh, it was trailing whitespace */
 217
 218                 /* Run `end' over a word, either whitespace separated or quoted */
 219                 if (*buf == '"' || *buf == '\'') {
 220                         int quote = *buf++;
 221                         for (end = buf ; *end && *end != quote ; end++)
 222                                 ;
 223                         if (!*end)
 224                                 return -EINVAL; /* unclosed quote */
 225                 } else {
 226                         for (end = buf ; *end && !isspace(*end) ; end++)
 227                                 ;
 228                         BUG_ON(end == buf);
 229                 }
 230                 /* Here `buf' is the start of the word, `end' is one past the end */
 231
 232                 if (nwords == maxwords)
 233                         return -EINVAL; /* ran out of words[] before bytes */
 234                 if (*end)
 235                         *end++ = '\0';  /* terminate the word */
 236                 words[nwords++] = buf;
 237                 buf = end;
 238         }
 239
 240         if (verbose) {
 241                 int i;
 242                 printk(KERN_INFO "%s: split into words:", __func__);
 243                 for (i = 0 ; i < nwords ; i++)
 244                         printk(" \"%s\"", words[i]);
 245                 printk("\n");
 246         }
 247
 248         return nwords;
 249 }
 250
 251 /*
 252  * Parse a single line number.  Note that the empty string ""
 253  * is treated as a special case and converted to zero, which
 254  * is later treated as a "don't care" value.
 255  */
 256 static inline int parse_lineno(const char *str, unsigned int *val)
 257 {
 258         char *end = NULL;
 259         BUG_ON(str == NULL);
 260         if (*str == '\0') {
 261                 *val = 0;
 262                 return 0;
 263         }
 264         *val = simple_strtoul(str, &end, 10);
 265         return end == NULL || end == str || *end != '\0' ? -EINVAL : 0;
 266 }
 267
 268 /*
 269  * Undo octal escaping in a string, inplace.  This is useful to
 270  * allow the user to express a query which matches a format
 271  * containing embedded spaces.
 272  */
 273 #define isodigit(c)             ((c) >= '0' && (c) <= '7')
 274 static char *unescape(char *str)
 275 {
 276         char *in = str;
 277         char *out = str;
 278
 279         while (*in) {
 280                 if (*in == '\\') {
 281                         if (in[1] == '\\') {
 282                                 *out++ = '\\';
 283                                 in += 2;
 284                                 continue;
 285                         } else if (in[1] == 't') {
 286                                 *out++ = '\t';
 287                                 in += 2;
 288                                 continue;
 289                         } else if (in[1] == 'n') {
 290                                 *out++ = '\n';
 291                                 in += 2;
 292                                 continue;
 293                         } else if (isodigit(in[1]) &&
 294                                  isodigit(in[2]) &&
 295                                  isodigit(in[3])) {
 296                                 *out++ = ((in[1] - '0')<<6) |
 297                                           ((in[2] - '0')<<3) |
 298                                           (in[3] - '0');
 299                                 in += 4;
 300                                 continue;
 301                         }
 302                 }
 303                 *out++ = *in++;
 304         }
 305         *out = '\0';
 306
 307         return str;
 308 }
 309
 310 /*
 311  * Parse words[] as a ddebug query specification, which is a series
 312  * of (keyword, value) pairs chosen from these possibilities:
 313  *
 314  * func <function-name>
 315  * file <full-pathname>
 316  * file <base-filename>
 317  * module <module-name>
 318  * format <escaped-string-to-find-in-format>
 319  * line <lineno>
 320  * line <first-lineno>-<last-lineno> // where either may be empty
 321  */
 322 static int ddebug_parse_query(char *words[], int nwords,
 323                                struct ddebug_query *query)
 324 {
 325         unsigned int i;
 326
 327         /* check we have an even number of words */
 328         if (nwords % 2 != 0)
 329                 return -EINVAL;
 330         memset(query, 0, sizeof(*query));
 331
 332         for (i = 0 ; i < nwords ; i += 2) {
 333                 if (!strcmp(words[i], "func"))
 334                         query->function = words[i+1];
 335                 else if (!strcmp(words[i], "file"))
 336                         query->filename = words[i+1];
 337                 else if (!strcmp(words[i], "module"))
 338                         query->module = words[i+1];
 339                 else if (!strcmp(words[i], "format"))
 340                         query->format = unescape(words[i+1]);
 341                 else if (!strcmp(words[i], "line")) {
 342                         char *first = words[i+1];
 343                         char *last = strchr(first, '-');
 344                         if (last)
 345                                 *last++ = '\0';
 346                         if (parse_lineno(first, &query->first_lineno) < 0)
 347                                 return -EINVAL;
 348                         if (last != NULL) {
 349                                 /* range <first>-<last> */
 350                                 if (parse_lineno(last, &query->last_lineno) < 0)
 351                                         return -EINVAL;
 352                         } else {
 353                                 query->last_lineno = query->first_lineno;
 354                         }
 355                 } else {
 356                         if (verbose)
 357                                 printk(KERN_ERR "%s: unknown keyword \"%s\"\n",
 358                                         __func__, words[i]);
 359                         return -EINVAL;
 360                 }
 361         }
 362
 363         if (verbose)
 364                 printk(KERN_INFO "%s: q->function=\"%s\" q->filename=\"%s\" "
 365                        "q->module=\"%s\" q->format=\"%s\" q->lineno=%u-%u\n",
 366                         __func__, query->function, query->filename,
 367                         query->module, query->format, query->first_lineno,
 368                         query->last_lineno);
 369
 370         return 0;
 371 }
 372
 373 /*
 374  * Parse `str' as a flags specification, format [-+=][p]+.
 375  * Sets up *maskp and *flagsp to be used when changing the
 376  * flags fields of matched _ddebug's.  Returns 0 on success
 377  * or <0 on error.
 378  */
 379 static int ddebug_parse_flags(const char *str, unsigned int *flagsp,
 380                                unsigned int *maskp)
 381 {
 382         unsigned flags = 0;
 383         int op = '=';
 384
 385         switch (*str) {
 386         case '+':
 387         case '-':
 388         case '=':
 389                 op = *str++;
 390                 break;
 391         default:
 392                 return -EINVAL;
 393         }
 394         if (verbose)
 395                 printk(KERN_INFO "%s: op='%c'\n", __func__, op);
 396
 397         for ( ; *str ; ++str) {
 398                 switch (*str) {
 399                 case 'p':
 400                         flags |= _DPRINTK_FLAGS_PRINT;
 401                         break;
 402                 default:
 403                         return -EINVAL;
 404                 }
 405         }
 406         if (flags == 0)
 407                 return -EINVAL;
 408         if (verbose)
 409                 printk(KERN_INFO "%s: flags=0x%x\n", __func__, flags);
 410
 411         /* calculate final *flagsp, *maskp according to mask and op */
 412         switch (op) {
 413         case '=':
 414                 *maskp = 0;
 415                 *flagsp = flags;
 416                 break;
 417         case '+':
 418                 *maskp = ~0U;
 419                 *flagsp = flags;
 420                 break;
 421         case '-':
 422                 *maskp = ~flags;
 423                 *flagsp = 0;
 424                 break;
 425         }
 426         if (verbose)
 427                 printk(KERN_INFO "%s: *flagsp=0x%x *maskp=0x%x\n",
 428                         __func__, *flagsp, *maskp);
 429         return 0;
 430 }
 431
 432 static int ddebug_exec_query(char *query_string)
 433 {
 434         unsigned int flags = 0, mask = 0;
 435         struct ddebug_query query;
 436 #define MAXWORDS 9
 437         int nwords;
 438         char *words[MAXWORDS];
 439
 440         nwords = ddebug_tokenize(query_string, words, MAXWORDS);
 441         if (nwords <= 0)
 442                 return -EINVAL;
 443         if (ddebug_parse_query(words, nwords-1, &query))
 444                 return -EINVAL;
 445         if (ddebug_parse_flags(words[nwords-1], &flags, &mask))
 446                 return -EINVAL;
 447
 448         /* actually go and implement the change */
 449         ddebug_change(&query, flags, mask);
 450         return 0;
 451 }
 452
 453 static __initdata char ddebug_setup_string[1024];
 454 static __init int ddebug_setup_query(char *str)
 455 {
 456         if (strlen(str) >= 1024) {
 457                 pr_warning("ddebug boot param string too large\n");
 458                 return 0;
 459         }
 460         strcpy(ddebug_setup_string, str);
 461         return 1;
 462 }
 463
 464 __setup("ddebug_query=", ddebug_setup_query);
 465
 466 /*
 467  * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
 468  * command text from userspace, parses and executes it.
 469  */
 470 static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
 471                                   size_t len, loff_t *offp)
 472 {
 473         char tmpbuf[256];
 474         int ret;
 475
 476         if (len == 0)
 477                 return 0;
 478         /* we don't check *offp -- multiple writes() are allowed */
 479         if (len > sizeof(tmpbuf)-1)
 480                 return -E2BIG;
 481         if (copy_from_user(tmpbuf, ubuf, len))
 482                 return -EFAULT;
 483         tmpbuf[len] = '\0';
 484         if (verbose)
 485                 printk(KERN_INFO "%s: read %d bytes from userspace\n",
 486                         __func__, (int)len);
 487
 488         ret = ddebug_exec_query(tmpbuf);
 489         if (ret)
 490                 return ret;
 491
 492         *offp += len;
 493         return len;
 494 }
 495
 496 /*
 497  * Set the iterator to point to the first _ddebug object
 498  * and return a pointer to that first object.  Returns
 499  * NULL if there are no _ddebugs at all.
 500  */
 501 static struct _ddebug *ddebug_iter_first(struct ddebug_iter *iter)
 502 {
 503         if (list_empty(&ddebug_tables)) {
 504                 iter->table = NULL;
 505                 iter->idx = 0;
 506                 return NULL;
 507         }
 508         iter->table = list_entry(ddebug_tables.next,
 509                                  struct ddebug_table, link);
 510         iter->idx = 0;
 511         return &iter->table->ddebugs[iter->idx];
 512 }
 513
 514 /*
 515  * Advance the iterator to point to the next _ddebug
 516  * object from the one the iterator currently points at,
 517  * and returns a pointer to the new _ddebug.  Returns
 518  * NULL if the iterator has seen all the _ddebugs.
 519  */
 520 static struct _ddebug *ddebug_iter_next(struct ddebug_iter *iter)
 521 {
 522         if (iter->table == NULL)
 523                 return NULL;
 524         if (++iter->idx == iter->table->num_ddebugs) {
 525                 /* iterate to next table */
 526                 iter->idx = 0;
 527                 if (list_is_last(&iter->table->link, &ddebug_tables)) {
 528                         iter->table = NULL;
 529                         return NULL;
 530                 }
 531                 iter->table = list_entry(iter->table->link.next,
 532                                          struct ddebug_table, link);
 533         }
 534         return &iter->table->ddebugs[iter->idx];
 535 }
 536
 537 /*
 538  * Seq_ops start method.  Called at the start of every
 539  * read() call from userspace.  Takes the ddebug_lock and
 540  * seeks the seq_file's iterator to the given position.
 541  */
 542 static void *ddebug_proc_start(struct seq_file *m, loff_t *pos)
 543 {
 544         struct ddebug_iter *iter = m->private;
 545         struct _ddebug *dp;
 546         int n = *pos;
 547
 548         if (verbose)
 549                 printk(KERN_INFO "%s: called m=%p *pos=%lld\n",
 550                         __func__, m, (unsigned long long)*pos);
 551
 552         mutex_lock(&ddebug_lock);
 553
 554         if (!n)
 555                 return SEQ_START_TOKEN;
 556         if (n < 0)
 557                 return NULL;
 558         dp = ddebug_iter_first(iter);
 559         while (dp != NULL && --n > 0)
 560                 dp = ddebug_iter_next(iter);
 561         return dp;
 562 }
 563
 564 /*
 565  * Seq_ops next method.  Called several times within a read()
 566  * call from userspace, with ddebug_lock held.  Walks to the
 567  * next _ddebug object with a special case for the header line.
 568  */
 569 static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
 570 {
 571         struct ddebug_iter *iter = m->private;
 572         struct _ddebug *dp;
 573
 574         if (verbose)
 575                 printk(KERN_INFO "%s: called m=%p p=%p *pos=%lld\n",
 576                         __func__, m, p, (unsigned long long)*pos);
 577
 578         if (p == SEQ_START_TOKEN)
 579                 dp = ddebug_iter_first(iter);
 580         else
 581                 dp = ddebug_iter_next(iter);
 582         ++*pos;
 583         return dp;
 584 }
 585
 586 /*
 587  * Seq_ops show method.  Called several times within a read()
 588  * call from userspace, with ddebug_lock held.  Formats the
 589  * current _ddebug as a single human-readable line, with a
 590  * special case for the header line.
 591  */
 592 static int ddebug_proc_show(struct seq_file *m, void *p)
 593 {
 594         struct ddebug_iter *iter = m->private;
 595         struct _ddebug *dp = p;
 596         char flagsbuf[8];
 597
 598         if (verbose)
 599                 printk(KERN_INFO "%s: called m=%p p=%p\n",
 600                         __func__, m, p);
 601
 602         if (p == SEQ_START_TOKEN) {
 603                 seq_puts(m,
 604                         "# filename:lineno [module]function flags format\n");
 605                 return 0;
 606         }
 607
 608         seq_printf(m, "%s:%u [%s]%s %s \"",
 609                    dp->filename, dp->lineno,
 610                    iter->table->mod_name, dp->function,
 611                    ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
 612         seq_escape(m, dp->format, "\t\r\n\"");
 613         seq_puts(m, "\"\n");
 614
 615         return 0;
 616 }
 617
 618 /*
 619  * Seq_ops stop method.  Called at the end of each read()
 620  * call from userspace.  Drops ddebug_lock.
 621  */
 622 static void ddebug_proc_stop(struct seq_file *m, void *p)
 623 {
 624         if (verbose)
 625                 printk(KERN_INFO "%s: called m=%p p=%p\n",
 626                         __func__, m, p);
 627         mutex_unlock(&ddebug_lock);
 628 }
 629
 630 static const struct seq_operations ddebug_proc_seqops = {
 631         .start = ddebug_proc_start,
 632         .next = ddebug_proc_next,
 633         .show = ddebug_proc_show,
 634         .stop = ddebug_proc_stop
 635 };
 636
 637 /*
 638  * File_ops->open method for <debugfs>/dynamic_debug/control.  Does the seq_file
 639  * setup dance, and also creates an iterator to walk the _ddebugs.
 640  * Note that we create a seq_file always, even for O_WRONLY files
 641  * where it's not needed, as doing so simplifies the ->release method.
 642  */
 643 static int ddebug_proc_open(struct inode *inode, struct file *file)
 644 {
 645         struct ddebug_iter *iter;
 646         int err;
 647
 648         if (verbose)
 649                 printk(KERN_INFO "%s: called\n", __func__);
 650
 651         iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 652         if (iter == NULL)
 653                 return -ENOMEM;
 654
 655         err = seq_open(file, &ddebug_proc_seqops);
 656         if (err) {
 657                 kfree(iter);
 658                 return err;
 659         }
 660         ((struct seq_file *) file->private_data)->private = iter;
 661         return 0;
 662 }
 663
 664 static const struct file_operations ddebug_proc_fops = {
 665         .owner = THIS_MODULE,
 666         .open = ddebug_proc_open,
 667         .read = seq_read,
 668         .llseek = seq_lseek,
 669         .release = seq_release_private,
 670         .write = ddebug_proc_write
 671 };
 672
 673 /*
 674  * Allocate a new ddebug_table for the given module
 675  * and add it to the global list.
 676  */
 677 int ddebug_add_module(struct _ddebug *tab, unsigned int n,
 678                              const char *name)
 679 {
 680         struct ddebug_table *dt;
 681         char *new_name;
 682
 683         dt = kzalloc(sizeof(*dt), GFP_KERNEL);
 684         if (dt == NULL)
 685                 return -ENOMEM;
 686         new_name = kstrdup(name, GFP_KERNEL);
 687         if (new_name == NULL) {
 688                 kfree(dt);
 689                 return -ENOMEM;
 690         }
 691         dt->mod_name = new_name;
 692         dt->num_ddebugs = n;
 693         dt->num_enabled = 0;
 694         dt->ddebugs = tab;
 695
 696         mutex_lock(&ddebug_lock);
 697         list_add_tail(&dt->link, &ddebug_tables);
 698         mutex_unlock(&ddebug_lock);
 699
 700         if (verbose)
 701                 printk(KERN_INFO "%u debug prints in module %s\n",
 702                                  n, dt->mod_name);
 703         return 0;
 704 }
 705 EXPORT_SYMBOL_GPL(ddebug_add_module);
 706
 707 static void ddebug_table_free(struct ddebug_table *dt)
 708 {
 709         list_del_init(&dt->link);
 710         kfree(dt->mod_name);
 711         kfree(dt);
 712 }
 713
 714 /*
 715  * Called in response to a module being unloaded.  Removes
 716  * any ddebug_table's which point at the module.
 717  */
 718 int ddebug_remove_module(const char *mod_name)
 719 {
 720         struct ddebug_table *dt, *nextdt;
 721         int ret = -ENOENT;
 722
 723         if (verbose)
 724                 printk(KERN_INFO "%s: removing module \"%s\"\n",
 725                                 __func__, mod_name);
 726
 727         mutex_lock(&ddebug_lock);
 728         list_for_each_entry_safe(dt, nextdt, &ddebug_tables, link) {
 729                 if (!strcmp(dt->mod_name, mod_name)) {
 730                         ddebug_table_free(dt);
 731                         ret = 0;
 732                 }
 733         }
 734         mutex_unlock(&ddebug_lock);
 735         return ret;
 736 }
 737 EXPORT_SYMBOL_GPL(ddebug_remove_module);
 738
 739 static void ddebug_remove_all_tables(void)
 740 {
 741         mutex_lock(&ddebug_lock);
 742         while (!list_empty(&ddebug_tables)) {
 743                 struct ddebug_table *dt = list_entry(ddebug_tables.next,
 744                                                       struct ddebug_table,
 745                                                       link);
 746                 ddebug_table_free(dt);
 747         }
 748         mutex_unlock(&ddebug_lock);
 749 }
 750
 751 static int __init dynamic_debug_init(void)
 752 {
 753         struct dentry *dir, *file;
 754         struct _ddebug *iter, *iter_start;
 755         const char *modname = NULL;
 756         int ret = 0;
 757         int n = 0;
 758
 759         dir = debugfs_create_dir("dynamic_debug", NULL);
 760         if (!dir)
 761                 return -ENOMEM;
 762         file = debugfs_create_file("control", 0644, dir, NULL,
 763                                         &ddebug_proc_fops);
 764         if (!file) {
 765                 debugfs_remove(dir);
 766                 return -ENOMEM;
 767         }
 768         if (__start___verbose != __stop___verbose) {
 769                 iter = __start___verbose;
 770                 modname = iter->modname;
 771                 iter_start = iter;
 772                 for (; iter < __stop___verbose; iter++) {
 773                         if (strcmp(modname, iter->modname)) {
 774                                 ret = ddebug_add_module(iter_start, n, modname);
 775                                 if (ret)
 776                                         goto out_free;
 777                                 n = 0;
 778                                 modname = iter->modname;
 779                                 iter_start = iter;
 780                         }
 781                         n++;
 782                 }
 783                 ret = ddebug_add_module(iter_start, n, modname);
 784         }
 785
 786         /* ddebug_query boot param got passed -> set it up */
 787         if (ddebug_setup_string[0] != '\0') {
 788                 ret = ddebug_exec_query(ddebug_setup_string);
 789                 if (ret)
 790                         pr_warning("Invalid ddebug boot param %s",
 791                                    ddebug_setup_string);
 792                 else
 793                         pr_info("ddebug initialized with string %s",
 794                                 ddebug_setup_string);
 795         }
 796
 797 out_free:
 798         if (ret) {
 799                 ddebug_remove_all_tables();
 800                 debugfs_remove(dir);
 801                 debugfs_remove(file);
 802         }
 803         return 0;
 804 }
 805 module_init(dynamic_debug_init);