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  * Copyright (C) 2011 Bart Van Assche.  All Rights Reserved.
  11  */
  12
  13 #define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
  14
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/moduleparam.h>
  18 #include <linux/kallsyms.h>
  19 #include <linux/types.h>
  20 #include <linux/mutex.h>
  21 #include <linux/proc_fs.h>
  22 #include <linux/seq_file.h>
  23 #include <linux/list.h>
  24 #include <linux/sysctl.h>
  25 #include <linux/ctype.h>
  26 #include <linux/string.h>
  27 #include <linux/uaccess.h>
  28 #include <linux/dynamic_debug.h>
  29 #include <linux/debugfs.h>
  30 #include <linux/slab.h>
  31 #include <linux/jump_label.h>
  32 #include <linux/hardirq.h>
  33 #include <linux/sched.h>
  34 #include <linux/device.h>
  35 #include <linux/netdevice.h>
  36
  37 extern struct _ddebug __start___verbose[];
  38 extern struct _ddebug __stop___verbose[];
  39
  40 struct ddebug_table {
  41         struct list_head link;
  42         char *mod_name;
  43         unsigned int num_ddebugs;
  44         struct _ddebug *ddebugs;
  45 };
  46
  47 struct ddebug_query {
  48         const char *filename;
  49         const char *module;
  50         const char *function;
  51         const char *format;
  52         unsigned int first_lineno, last_lineno;
  53 };
  54
  55 struct ddebug_iter {
  56         struct ddebug_table *table;
  57         unsigned int idx;
  58 };
  59
  60 static DEFINE_MUTEX(ddebug_lock);
  61 static LIST_HEAD(ddebug_tables);
  62 static int verbose = 0;
  63
  64 /* Return the last part of a pathname */
  65 static inline const char *basename(const char *path)
  66 {
  67         const char *tail = strrchr(path, '/');
  68         return tail ? tail+1 : path;
  69 }
  70
  71 static struct { unsigned flag:8; char opt_char; } opt_array[] = {
  72         { _DPRINTK_FLAGS_PRINT, 'p' },
  73         { _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
  74         { _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
  75         { _DPRINTK_FLAGS_INCL_LINENO, 'l' },
  76         { _DPRINTK_FLAGS_INCL_TID, 't' },
  77 };
  78
  79 /* format a string into buf[] which describes the _ddebug's flags */
  80 static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
  81                                     size_t maxlen)
  82 {
  83         char *p = buf;
  84         int i;
  85
  86         BUG_ON(maxlen < 4);
  87         for (i = 0; i < ARRAY_SIZE(opt_array); ++i)
  88                 if (dp->flags & opt_array[i].flag)
  89                         *p++ = opt_array[i].opt_char;
  90         if (p == buf)
  91                 *p++ = '-';
  92         *p = '\0';
  93
  94         return buf;
  95 }
  96
  97 /*
  98  * Search the tables for _ddebug's which match the given
  99  * `query' and apply the `flags' and `mask' to them.  Tells
 100  * the user which ddebug's were changed, or whether none
 101  * were matched.
 102  */
 103 static void ddebug_change(const struct ddebug_query *query,
 104                            unsigned int flags, unsigned int mask)
 105 {
 106         int i;
 107         struct ddebug_table *dt;
 108         unsigned int newflags;
 109         unsigned int nfound = 0;
 110         char flagbuf[8];
 111
 112         /* search for matching ddebugs */
 113         mutex_lock(&ddebug_lock);
 114         list_for_each_entry(dt, &ddebug_tables, link) {
 115
 116                 /* match against the module name */
 117                 if (query->module != NULL &&
 118                     strcmp(query->module, dt->mod_name))
 119                         continue;
 120
 121                 for (i = 0 ; i < dt->num_ddebugs ; i++) {
 122                         struct _ddebug *dp = &dt->ddebugs[i];
 123
 124                         /* match against the source filename */
 125                         if (query->filename != NULL &&
 126                             strcmp(query->filename, dp->filename) &&
 127                             strcmp(query->filename, basename(dp->filename)))
 128                                 continue;
 129
 130                         /* match against the function */
 131                         if (query->function != NULL &&
 132                             strcmp(query->function, dp->function))
 133                                 continue;
 134
 135                         /* match against the format */
 136                         if (query->format != NULL &&
 137                             strstr(dp->format, query->format) == NULL)
 138                                 continue;
 139
 140                         /* match against the line number range */
 141                         if (query->first_lineno &&
 142                             dp->lineno < query->first_lineno)
 143                                 continue;
 144                         if (query->last_lineno &&
 145                             dp->lineno > query->last_lineno)
 146                                 continue;
 147
 148                         nfound++;
 149
 150                         newflags = (dp->flags & mask) | flags;
 151                         if (newflags == dp->flags)
 152                                 continue;
 153                         dp->flags = newflags;
 154                         if (newflags)
 155                                 dp->enabled = 1;
 156                         else
 157                                 dp->enabled = 0;
 158                         if (verbose)
 159                                 pr_info("changed %s:%d [%s]%s %s\n",
 160                                         dp->filename, dp->lineno,
 161                                         dt->mod_name, dp->function,
 162                                         ddebug_describe_flags(dp, flagbuf,
 163                                                         sizeof(flagbuf)));
 164                 }
 165         }
 166         mutex_unlock(&ddebug_lock);
 167
 168         if (!nfound && verbose)
 169                 pr_info("no matches for query\n");
 170 }
 171
 172 /*
 173  * Split the buffer `buf' into space-separated words.
 174  * Handles simple " and ' quoting, i.e. without nested,
 175  * embedded or escaped \".  Return the number of words
 176  * or <0 on error.
 177  */
 178 static int ddebug_tokenize(char *buf, char *words[], int maxwords)
 179 {
 180         int nwords = 0;
 181
 182         while (*buf) {
 183                 char *end;
 184
 185                 /* Skip leading whitespace */
 186                 buf = skip_spaces(buf);
 187                 if (!*buf)
 188                         break;  /* oh, it was trailing whitespace */
 189
 190                 /* Run `end' over a word, either whitespace separated or quoted */
 191                 if (*buf == '"' || *buf == '\'') {
 192                         int quote = *buf++;
 193                         for (end = buf ; *end && *end != quote ; end++)
 194                                 ;
 195                         if (!*end)
 196                                 return -EINVAL; /* unclosed quote */
 197                 } else {
 198                         for (end = buf ; *end && !isspace(*end) ; end++)
 199                                 ;
 200                         BUG_ON(end == buf);
 201                 }
 202                 /* Here `buf' is the start of the word, `end' is one past the end */
 203
 204                 if (nwords == maxwords)
 205                         return -EINVAL; /* ran out of words[] before bytes */
 206                 if (*end)
 207                         *end++ = '\0';  /* terminate the word */
 208                 words[nwords++] = buf;
 209                 buf = end;
 210         }
 211
 212         if (verbose) {
 213                 int i;
 214                 pr_info("split into words:");
 215                 for (i = 0 ; i < nwords ; i++)
 216                         pr_cont(" \"%s\"", words[i]);
 217                 pr_cont("\n");
 218         }
 219
 220         return nwords;
 221 }
 222
 223 /*
 224  * Parse a single line number.  Note that the empty string ""
 225  * is treated as a special case and converted to zero, which
 226  * is later treated as a "don't care" value.
 227  */
 228 static inline int parse_lineno(const char *str, unsigned int *val)
 229 {
 230         char *end = NULL;
 231         BUG_ON(str == NULL);
 232         if (*str == '\0') {
 233                 *val = 0;
 234                 return 0;
 235         }
 236         *val = simple_strtoul(str, &end, 10);
 237         return end == NULL || end == str || *end != '\0' ? -EINVAL : 0;
 238 }
 239
 240 /*
 241  * Undo octal escaping in a string, inplace.  This is useful to
 242  * allow the user to express a query which matches a format
 243  * containing embedded spaces.
 244  */
 245 #define isodigit(c)             ((c) >= '0' && (c) <= '7')
 246 static char *unescape(char *str)
 247 {
 248         char *in = str;
 249         char *out = str;
 250
 251         while (*in) {
 252                 if (*in == '\\') {
 253                         if (in[1] == '\\') {
 254                                 *out++ = '\\';
 255                                 in += 2;
 256                                 continue;
 257                         } else if (in[1] == 't') {
 258                                 *out++ = '\t';
 259                                 in += 2;
 260                                 continue;
 261                         } else if (in[1] == 'n') {
 262                                 *out++ = '\n';
 263                                 in += 2;
 264                                 continue;
 265                         } else if (isodigit(in[1]) &&
 266                                  isodigit(in[2]) &&
 267                                  isodigit(in[3])) {
 268                                 *out++ = ((in[1] - '0')<<6) |
 269                                           ((in[2] - '0')<<3) |
 270                                           (in[3] - '0');
 271                                 in += 4;
 272                                 continue;
 273                         }
 274                 }
 275                 *out++ = *in++;
 276         }
 277         *out = '\0';
 278
 279         return str;
 280 }
 281
 282 /*
 283  * Parse words[] as a ddebug query specification, which is a series
 284  * of (keyword, value) pairs chosen from these possibilities:
 285  *
 286  * func <function-name>
 287  * file <full-pathname>
 288  * file <base-filename>
 289  * module <module-name>
 290  * format <escaped-string-to-find-in-format>
 291  * line <lineno>
 292  * line <first-lineno>-<last-lineno> // where either may be empty
 293  */
 294 static int ddebug_parse_query(char *words[], int nwords,
 295                                struct ddebug_query *query)
 296 {
 297         unsigned int i;
 298
 299         /* check we have an even number of words */
 300         if (nwords % 2 != 0)
 301                 return -EINVAL;
 302         memset(query, 0, sizeof(*query));
 303
 304         for (i = 0 ; i < nwords ; i += 2) {
 305                 if (!strcmp(words[i], "func"))
 306                         query->function = words[i+1];
 307                 else if (!strcmp(words[i], "file"))
 308                         query->filename = words[i+1];
 309                 else if (!strcmp(words[i], "module"))
 310                         query->module = words[i+1];
 311                 else if (!strcmp(words[i], "format"))
 312                         query->format = unescape(words[i+1]);
 313                 else if (!strcmp(words[i], "line")) {
 314                         char *first = words[i+1];
 315                         char *last = strchr(first, '-');
 316                         if (last)
 317                                 *last++ = '\0';
 318                         if (parse_lineno(first, &query->first_lineno) < 0)
 319                                 return -EINVAL;
 320                         if (last != NULL) {
 321                                 /* range <first>-<last> */
 322                                 if (parse_lineno(last, &query->last_lineno) < 0)
 323                                         return -EINVAL;
 324                         } else {
 325                                 query->last_lineno = query->first_lineno;
 326                         }
 327                 } else {
 328                         if (verbose)
 329                                 pr_err("unknown keyword \"%s\"\n", words[i]);
 330                         return -EINVAL;
 331                 }
 332         }
 333
 334         if (verbose)
 335                 pr_info("q->function=\"%s\" q->filename=\"%s\" "
 336                         "q->module=\"%s\" q->format=\"%s\" q->lineno=%u-%u\n",
 337                         query->function, query->filename,
 338                         query->module, query->format, query->first_lineno,
 339                         query->last_lineno);
 340
 341         return 0;
 342 }
 343
 344 /*
 345  * Parse `str' as a flags specification, format [-+=][p]+.
 346  * Sets up *maskp and *flagsp to be used when changing the
 347  * flags fields of matched _ddebug's.  Returns 0 on success
 348  * or <0 on error.
 349  */
 350 static int ddebug_parse_flags(const char *str, unsigned int *flagsp,
 351                                unsigned int *maskp)
 352 {
 353         unsigned flags = 0;
 354         int op = '=', i;
 355
 356         switch (*str) {
 357         case '+':
 358         case '-':
 359         case '=':
 360                 op = *str++;
 361                 break;
 362         default:
 363                 return -EINVAL;
 364         }
 365         if (verbose)
 366                 pr_info("op='%c'\n", op);
 367
 368         for ( ; *str ; ++str) {
 369                 for (i = ARRAY_SIZE(opt_array) - 1; i >= 0; i--) {
 370                         if (*str == opt_array[i].opt_char) {
 371                                 flags |= opt_array[i].flag;
 372                                 break;
 373                         }
 374                 }
 375                 if (i < 0)
 376                         return -EINVAL;
 377         }
 378         if (flags == 0)
 379                 return -EINVAL;
 380         if (verbose)
 381                 pr_info("flags=0x%x\n", flags);
 382
 383         /* calculate final *flagsp, *maskp according to mask and op */
 384         switch (op) {
 385         case '=':
 386                 *maskp = 0;
 387                 *flagsp = flags;
 388                 break;
 389         case '+':
 390                 *maskp = ~0U;
 391                 *flagsp = flags;
 392                 break;
 393         case '-':
 394                 *maskp = ~flags;
 395                 *flagsp = 0;
 396                 break;
 397         }
 398         if (verbose)
 399                 pr_info("*flagsp=0x%x *maskp=0x%x\n", *flagsp, *maskp);
 400         return 0;
 401 }
 402
 403 static int ddebug_exec_query(char *query_string)
 404 {
 405         unsigned int flags = 0, mask = 0;
 406         struct ddebug_query query;
 407 #define MAXWORDS 9
 408         int nwords;
 409         char *words[MAXWORDS];
 410
 411         nwords = ddebug_tokenize(query_string, words, MAXWORDS);
 412         if (nwords <= 0)
 413                 return -EINVAL;
 414         if (ddebug_parse_query(words, nwords-1, &query))
 415                 return -EINVAL;
 416         if (ddebug_parse_flags(words[nwords-1], &flags, &mask))
 417                 return -EINVAL;
 418
 419         /* actually go and implement the change */
 420         ddebug_change(&query, flags, mask);
 421         return 0;
 422 }
 423
 424 #define PREFIX_SIZE 64
 425
 426 static int remaining(int wrote)
 427 {
 428         if (PREFIX_SIZE - wrote > 0)
 429                 return PREFIX_SIZE - wrote;
 430         return 0;
 431 }
 432
 433 static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
 434 {
 435         int pos_after_tid;
 436         int pos = 0;
 437
 438         pos += snprintf(buf + pos, remaining(pos), "%s", KERN_DEBUG);
 439         if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
 440                 if (in_interrupt())
 441                         pos += snprintf(buf + pos, remaining(pos), "%s ",
 442                                                 "<intr>");
 443                 else
 444                         pos += snprintf(buf + pos, remaining(pos), "[%d] ",
 445                                                 task_pid_vnr(current));
 446         }
 447         pos_after_tid = pos;
 448         if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
 449                 pos += snprintf(buf + pos, remaining(pos), "%s:",
 450                                         desc->modname);
 451         if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
 452                 pos += snprintf(buf + pos, remaining(pos), "%s:",
 453                                         desc->function);
 454         if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
 455                 pos += snprintf(buf + pos, remaining(pos), "%d:", desc->lineno);
 456         if (pos - pos_after_tid)
 457                 pos += snprintf(buf + pos, remaining(pos), " ");
 458         if (pos >= PREFIX_SIZE)
 459                 buf[PREFIX_SIZE - 1] = '\0';
 460
 461         return buf;
 462 }
 463
 464 int __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
 465 {
 466         va_list args;
 467         int res;
 468         struct va_format vaf;
 469         char buf[PREFIX_SIZE];
 470
 471         BUG_ON(!descriptor);
 472         BUG_ON(!fmt);
 473
 474         va_start(args, fmt);
 475         vaf.fmt = fmt;
 476         vaf.va = &args;
 477         res = printk("%s%pV", dynamic_emit_prefix(descriptor, buf), &vaf);
 478         va_end(args);
 479
 480         return res;
 481 }
 482 EXPORT_SYMBOL(__dynamic_pr_debug);
 483
 484 int __dynamic_dev_dbg(struct _ddebug *descriptor,
 485                       const struct device *dev, const char *fmt, ...)
 486 {
 487         struct va_format vaf;
 488         va_list args;
 489         int res;
 490         char buf[PREFIX_SIZE];
 491
 492         BUG_ON(!descriptor);
 493         BUG_ON(!fmt);
 494
 495         va_start(args, fmt);
 496         vaf.fmt = fmt;
 497         vaf.va = &args;
 498         res = __dev_printk(dynamic_emit_prefix(descriptor, buf), dev, &vaf);
 499         va_end(args);
 500
 501         return res;
 502 }
 503 EXPORT_SYMBOL(__dynamic_dev_dbg);
 504
 505 #ifdef CONFIG_NET
 506
 507 int __dynamic_netdev_dbg(struct _ddebug *descriptor,
 508                       const struct net_device *dev, const char *fmt, ...)
 509 {
 510         struct va_format vaf;
 511         va_list args;
 512         int res;
 513         char buf[PREFIX_SIZE];
 514
 515         BUG_ON(!descriptor);
 516         BUG_ON(!fmt);
 517
 518         va_start(args, fmt);
 519         vaf.fmt = fmt;
 520         vaf.va = &args;
 521         res = __netdev_printk(dynamic_emit_prefix(descriptor, buf), dev, &vaf);
 522         va_end(args);
 523
 524         return res;
 525 }
 526 EXPORT_SYMBOL(__dynamic_netdev_dbg);
 527
 528 #endif
 529
 530 static __initdata char ddebug_setup_string[1024];
 531 static __init int ddebug_setup_query(char *str)
 532 {
 533         if (strlen(str) >= 1024) {
 534                 pr_warn("ddebug boot param string too large\n");
 535                 return 0;
 536         }
 537         strcpy(ddebug_setup_string, str);
 538         return 1;
 539 }
 540
 541 __setup("ddebug_query=", ddebug_setup_query);
 542
 543 /*
 544  * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
 545  * command text from userspace, parses and executes it.
 546  */
 547 static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
 548                                   size_t len, loff_t *offp)
 549 {
 550         char tmpbuf[256];
 551         int ret;
 552
 553         if (len == 0)
 554                 return 0;
 555         /* we don't check *offp -- multiple writes() are allowed */
 556         if (len > sizeof(tmpbuf)-1)
 557                 return -E2BIG;
 558         if (copy_from_user(tmpbuf, ubuf, len))
 559                 return -EFAULT;
 560         tmpbuf[len] = '\0';
 561         if (verbose)
 562                 pr_info("read %d bytes from userspace\n", (int)len);
 563
 564         ret = ddebug_exec_query(tmpbuf);
 565         if (ret)
 566                 return ret;
 567
 568         *offp += len;
 569         return len;
 570 }
 571
 572 /*
 573  * Set the iterator to point to the first _ddebug object
 574  * and return a pointer to that first object.  Returns
 575  * NULL if there are no _ddebugs at all.
 576  */
 577 static struct _ddebug *ddebug_iter_first(struct ddebug_iter *iter)
 578 {
 579         if (list_empty(&ddebug_tables)) {
 580                 iter->table = NULL;
 581                 iter->idx = 0;
 582                 return NULL;
 583         }
 584         iter->table = list_entry(ddebug_tables.next,
 585                                  struct ddebug_table, link);
 586         iter->idx = 0;
 587         return &iter->table->ddebugs[iter->idx];
 588 }
 589
 590 /*
 591  * Advance the iterator to point to the next _ddebug
 592  * object from the one the iterator currently points at,
 593  * and returns a pointer to the new _ddebug.  Returns
 594  * NULL if the iterator has seen all the _ddebugs.
 595  */
 596 static struct _ddebug *ddebug_iter_next(struct ddebug_iter *iter)
 597 {
 598         if (iter->table == NULL)
 599                 return NULL;
 600         if (++iter->idx == iter->table->num_ddebugs) {
 601                 /* iterate to next table */
 602                 iter->idx = 0;
 603                 if (list_is_last(&iter->table->link, &ddebug_tables)) {
 604                         iter->table = NULL;
 605                         return NULL;
 606                 }
 607                 iter->table = list_entry(iter->table->link.next,
 608                                          struct ddebug_table, link);
 609         }
 610         return &iter->table->ddebugs[iter->idx];
 611 }
 612
 613 /*
 614  * Seq_ops start method.  Called at the start of every
 615  * read() call from userspace.  Takes the ddebug_lock and
 616  * seeks the seq_file's iterator to the given position.
 617  */
 618 static void *ddebug_proc_start(struct seq_file *m, loff_t *pos)
 619 {
 620         struct ddebug_iter *iter = m->private;
 621         struct _ddebug *dp;
 622         int n = *pos;
 623
 624         if (verbose)
 625                 pr_info("called m=%p *pos=%lld\n", m, (unsigned long long)*pos);
 626
 627         mutex_lock(&ddebug_lock);
 628
 629         if (!n)
 630                 return SEQ_START_TOKEN;
 631         if (n < 0)
 632                 return NULL;
 633         dp = ddebug_iter_first(iter);
 634         while (dp != NULL && --n > 0)
 635                 dp = ddebug_iter_next(iter);
 636         return dp;
 637 }
 638
 639 /*
 640  * Seq_ops next method.  Called several times within a read()
 641  * call from userspace, with ddebug_lock held.  Walks to the
 642  * next _ddebug object with a special case for the header line.
 643  */
 644 static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
 645 {
 646         struct ddebug_iter *iter = m->private;
 647         struct _ddebug *dp;
 648
 649         if (verbose)
 650                 pr_info("called m=%p p=%p *pos=%lld\n",
 651                         m, p, (unsigned long long)*pos);
 652
 653         if (p == SEQ_START_TOKEN)
 654                 dp = ddebug_iter_first(iter);
 655         else
 656                 dp = ddebug_iter_next(iter);
 657         ++*pos;
 658         return dp;
 659 }
 660
 661 /*
 662  * Seq_ops show method.  Called several times within a read()
 663  * call from userspace, with ddebug_lock held.  Formats the
 664  * current _ddebug as a single human-readable line, with a
 665  * special case for the header line.
 666  */
 667 static int ddebug_proc_show(struct seq_file *m, void *p)
 668 {
 669         struct ddebug_iter *iter = m->private;
 670         struct _ddebug *dp = p;
 671         char flagsbuf[8];
 672
 673         if (verbose)
 674                 pr_info("called m=%p p=%p\n", m, p);
 675
 676         if (p == SEQ_START_TOKEN) {
 677                 seq_puts(m,
 678                         "# filename:lineno [module]function flags format\n");
 679                 return 0;
 680         }
 681
 682         seq_printf(m, "%s:%u [%s]%s %s \"",
 683                    dp->filename, dp->lineno,
 684                    iter->table->mod_name, dp->function,
 685                    ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
 686         seq_escape(m, dp->format, "\t\r\n\"");
 687         seq_puts(m, "\"\n");
 688
 689         return 0;
 690 }
 691
 692 /*
 693  * Seq_ops stop method.  Called at the end of each read()
 694  * call from userspace.  Drops ddebug_lock.
 695  */
 696 static void ddebug_proc_stop(struct seq_file *m, void *p)
 697 {
 698         if (verbose)
 699                 pr_info("called m=%p p=%p\n", m, p);
 700         mutex_unlock(&ddebug_lock);
 701 }
 702
 703 static const struct seq_operations ddebug_proc_seqops = {
 704         .start = ddebug_proc_start,
 705         .next = ddebug_proc_next,
 706         .show = ddebug_proc_show,
 707         .stop = ddebug_proc_stop
 708 };
 709
 710 /*
 711  * File_ops->open method for <debugfs>/dynamic_debug/control.  Does the seq_file
 712  * setup dance, and also creates an iterator to walk the _ddebugs.
 713  * Note that we create a seq_file always, even for O_WRONLY files
 714  * where it's not needed, as doing so simplifies the ->release method.
 715  */
 716 static int ddebug_proc_open(struct inode *inode, struct file *file)
 717 {
 718         struct ddebug_iter *iter;
 719         int err;
 720
 721         if (verbose)
 722                 pr_info("called\n");
 723
 724         iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 725         if (iter == NULL)
 726                 return -ENOMEM;
 727
 728         err = seq_open(file, &ddebug_proc_seqops);
 729         if (err) {
 730                 kfree(iter);
 731                 return err;
 732         }
 733         ((struct seq_file *) file->private_data)->private = iter;
 734         return 0;
 735 }
 736
 737 static const struct file_operations ddebug_proc_fops = {
 738         .owner = THIS_MODULE,
 739         .open = ddebug_proc_open,
 740         .read = seq_read,
 741         .llseek = seq_lseek,
 742         .release = seq_release_private,
 743         .write = ddebug_proc_write
 744 };
 745
 746 /*
 747  * Allocate a new ddebug_table for the given module
 748  * and add it to the global list.
 749  */
 750 int ddebug_add_module(struct _ddebug *tab, unsigned int n,
 751                              const char *name)
 752 {
 753         struct ddebug_table *dt;
 754         char *new_name;
 755
 756         dt = kzalloc(sizeof(*dt), GFP_KERNEL);
 757         if (dt == NULL)
 758                 return -ENOMEM;
 759         new_name = kstrdup(name, GFP_KERNEL);
 760         if (new_name == NULL) {
 761                 kfree(dt);
 762                 return -ENOMEM;
 763         }
 764         dt->mod_name = new_name;
 765         dt->num_ddebugs = n;
 766         dt->ddebugs = tab;
 767
 768         mutex_lock(&ddebug_lock);
 769         list_add_tail(&dt->link, &ddebug_tables);
 770         mutex_unlock(&ddebug_lock);
 771
 772         if (verbose)
 773                 pr_info("%u debug prints in module %s\n", n, dt->mod_name);
 774         return 0;
 775 }
 776 EXPORT_SYMBOL_GPL(ddebug_add_module);
 777
 778 static void ddebug_table_free(struct ddebug_table *dt)
 779 {
 780         list_del_init(&dt->link);
 781         kfree(dt->mod_name);
 782         kfree(dt);
 783 }
 784
 785 /*
 786  * Called in response to a module being unloaded.  Removes
 787  * any ddebug_table's which point at the module.
 788  */
 789 int ddebug_remove_module(const char *mod_name)
 790 {
 791         struct ddebug_table *dt, *nextdt;
 792         int ret = -ENOENT;
 793
 794         if (verbose)
 795                 pr_info("removing module \"%s\"\n", mod_name);
 796
 797         mutex_lock(&ddebug_lock);
 798         list_for_each_entry_safe(dt, nextdt, &ddebug_tables, link) {
 799                 if (!strcmp(dt->mod_name, mod_name)) {
 800                         ddebug_table_free(dt);
 801                         ret = 0;
 802                 }
 803         }
 804         mutex_unlock(&ddebug_lock);
 805         return ret;
 806 }
 807 EXPORT_SYMBOL_GPL(ddebug_remove_module);
 808
 809 static void ddebug_remove_all_tables(void)
 810 {
 811         mutex_lock(&ddebug_lock);
 812         while (!list_empty(&ddebug_tables)) {
 813                 struct ddebug_table *dt = list_entry(ddebug_tables.next,
 814                                                       struct ddebug_table,
 815                                                       link);
 816                 ddebug_table_free(dt);
 817         }
 818         mutex_unlock(&ddebug_lock);
 819 }
 820
 821 static __initdata int ddebug_init_success;
 822
 823 static int __init dynamic_debug_init_debugfs(void)
 824 {
 825         struct dentry *dir, *file;
 826
 827         if (!ddebug_init_success)
 828                 return -ENODEV;
 829
 830         dir = debugfs_create_dir("dynamic_debug", NULL);
 831         if (!dir)
 832                 return -ENOMEM;
 833         file = debugfs_create_file("control", 0644, dir, NULL,
 834                                         &ddebug_proc_fops);
 835         if (!file) {
 836                 debugfs_remove(dir);
 837                 return -ENOMEM;
 838         }
 839         return 0;
 840 }
 841
 842 static int __init dynamic_debug_init(void)
 843 {
 844         struct _ddebug *iter, *iter_start;
 845         const char *modname = NULL;
 846         int ret = 0;
 847         int n = 0;
 848
 849         if (__start___verbose != __stop___verbose) {
 850                 iter = __start___verbose;
 851                 modname = iter->modname;
 852                 iter_start = iter;
 853                 for (; iter < __stop___verbose; iter++) {
 854                         if (strcmp(modname, iter->modname)) {
 855                                 ret = ddebug_add_module(iter_start, n, modname);
 856                                 if (ret)
 857                                         goto out_free;
 858                                 n = 0;
 859                                 modname = iter->modname;
 860                                 iter_start = iter;
 861                         }
 862                         n++;
 863                 }
 864                 ret = ddebug_add_module(iter_start, n, modname);
 865         }
 866
 867         /* ddebug_query boot param got passed -> set it up */
 868         if (ddebug_setup_string[0] != '\0') {
 869                 ret = ddebug_exec_query(ddebug_setup_string);
 870                 if (ret)
 871                         pr_warn("Invalid ddebug boot param %s",
 872                                 ddebug_setup_string);
 873                 else
 874                         pr_info("ddebug initialized with string %s",
 875                                 ddebug_setup_string);
 876         }
 877
 878 out_free:
 879         if (ret)
 880                 ddebug_remove_all_tables();
 881         else
 882                 ddebug_init_success = 1;
 883         return 0;
 884 }
 885 /* Allow early initialization for boot messages via boot param */
 886 arch_initcall(dynamic_debug_init);
 887 /* Debugfs setup must be done later */
 888 module_init(dynamic_debug_init_debugfs);