kernel/kallsyms.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
   4  *
   5  * Rewritten and vastly simplified by Rusty Russell for in-kernel
   6  * module loader:
   7  *   Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
   8  *
   9  * ChangeLog:
  10  *
  11  * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
  12  *      Changed the compression method from stem compression to "table lookup"
  13  *      compression (see scripts/kallsyms.c for a more complete description)
  14  */
  15 #include <linux/kallsyms.h>
  16 #include <linux/init.h>
  17 #include <linux/seq_file.h>
  18 #include <linux/fs.h>
  19 #include <linux/kdb.h>
  20 #include <linux/err.h>
  21 #include <linux/proc_fs.h>
  22 #include <linux/sched.h>        /* for cond_resched */
  23 #include <linux/ctype.h>
  24 #include <linux/slab.h>
  25 #include <linux/filter.h>
  26 #include <linux/ftrace.h>
  27 #include <linux/compiler.h>
  28
  29 /*
  30  * These will be re-linked against their real values
  31  * during the second link stage.
  32  */
  33 extern const unsigned long kallsyms_addresses[] __weak;
  34 extern const int kallsyms_offsets[] __weak;
  35 extern const u8 kallsyms_names[] __weak;
  36
  37 /*
  38  * Tell the compiler that the count isn't in the small data section if the arch
  39  * has one (eg: FRV).
  40  */
  41 extern const unsigned int kallsyms_num_syms
  42 __attribute__((weak, section(".rodata")));
  43
  44 extern const unsigned long kallsyms_relative_base
  45 __attribute__((weak, section(".rodata")));
  46
  47 extern const u8 kallsyms_token_table[] __weak;
  48 extern const u16 kallsyms_token_index[] __weak;
  49
  50 extern const unsigned int kallsyms_markers[] __weak;
  51
  52 /*
  53  * Expand a compressed symbol data into the resulting uncompressed string,
  54  * if uncompressed string is too long (>= maxlen), it will be truncated,
  55  * given the offset to where the symbol is in the compressed stream.
  56  */
  57 static unsigned int kallsyms_expand_symbol(unsigned int off,
  58                                            char *result, size_t maxlen)
  59 {
  60         int len, skipped_first = 0;
  61         const u8 *tptr, *data;
  62
  63         /* Get the compressed symbol length from the first symbol byte. */
  64         data = &kallsyms_names[off];
  65         len = *data;
  66         data++;
  67
  68         /*
  69          * Update the offset to return the offset for the next symbol on
  70          * the compressed stream.
  71          */
  72         off += len + 1;
  73
  74         /*
  75          * For every byte on the compressed symbol data, copy the table
  76          * entry for that byte.
  77          */
  78         while (len) {
  79                 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
  80                 data++;
  81                 len--;
  82
  83                 while (*tptr) {
  84                         if (skipped_first) {
  85                                 if (maxlen <= 1)
  86                                         goto tail;
  87                                 *result = *tptr;
  88                                 result++;
  89                                 maxlen--;
  90                         } else
  91                                 skipped_first = 1;
  92                         tptr++;
  93                 }
  94         }
  95
  96 tail:
  97         if (maxlen)
  98                 *result = '\0';
  99
 100         /* Return to offset to the next symbol. */
 101         return off;
 102 }
 103
 104 /*
 105  * Get symbol type information. This is encoded as a single char at the
 106  * beginning of the symbol name.
 107  */
 108 static char kallsyms_get_symbol_type(unsigned int off)
 109 {
 110         /*
 111          * Get just the first code, look it up in the token table,
 112          * and return the first char from this token.
 113          */
 114         return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
 115 }
 116
 117
 118 /*
 119  * Find the offset on the compressed stream given and index in the
 120  * kallsyms array.
 121  */
 122 static unsigned int get_symbol_offset(unsigned long pos)
 123 {
 124         const u8 *name;
 125         int i;
 126
 127         /*
 128          * Use the closest marker we have. We have markers every 256 positions,
 129          * so that should be close enough.
 130          */
 131         name = &kallsyms_names[kallsyms_markers[pos >> 8]];
 132
 133         /*
 134          * Sequentially scan all the symbols up to the point we're searching
 135          * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
 136          * so we just need to add the len to the current pointer for every
 137          * symbol we wish to skip.
 138          */
 139         for (i = 0; i < (pos & 0xFF); i++)
 140                 name = name + (*name) + 1;
 141
 142         return name - kallsyms_names;
 143 }
 144
 145 static unsigned long kallsyms_sym_address(int idx)
 146 {
 147         if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
 148                 return kallsyms_addresses[idx];
 149
 150         /* values are unsigned offsets if --absolute-percpu is not in effect */
 151         if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
 152                 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
 153
 154         /* ...otherwise, positive offsets are absolute values */
 155         if (kallsyms_offsets[idx] >= 0)
 156                 return kallsyms_offsets[idx];
 157
 158         /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
 159         return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
 160 }
 161
 162 /* Lookup the address for this symbol. Returns 0 if not found. */
 163 unsigned long kallsyms_lookup_name(const char *name)
 164 {
 165         char namebuf[KSYM_NAME_LEN];
 166         unsigned long i;
 167         unsigned int off;
 168
 169         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 170                 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 171
 172                 if (strcmp(namebuf, name) == 0)
 173                         return kallsyms_sym_address(i);
 174         }
 175         return module_kallsyms_lookup_name(name);
 176 }
 177 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
 178
 179 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 180                                       unsigned long),
 181                             void *data)
 182 {
 183         char namebuf[KSYM_NAME_LEN];
 184         unsigned long i;
 185         unsigned int off;
 186         int ret;
 187
 188         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 189                 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 190                 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
 191                 if (ret != 0)
 192                         return ret;
 193         }
 194         return module_kallsyms_on_each_symbol(fn, data);
 195 }
 196 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
 197
 198 static unsigned long get_symbol_pos(unsigned long addr,
 199                                     unsigned long *symbolsize,
 200                                     unsigned long *offset)
 201 {
 202         unsigned long symbol_start = 0, symbol_end = 0;
 203         unsigned long i, low, high, mid;
 204
 205         /* This kernel should never had been booted. */
 206         if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
 207                 BUG_ON(!kallsyms_addresses);
 208         else
 209                 BUG_ON(!kallsyms_offsets);
 210
 211         /* Do a binary search on the sorted kallsyms_addresses array. */
 212         low = 0;
 213         high = kallsyms_num_syms;
 214
 215         while (high - low > 1) {
 216                 mid = low + (high - low) / 2;
 217                 if (kallsyms_sym_address(mid) <= addr)
 218                         low = mid;
 219                 else
 220                         high = mid;
 221         }
 222
 223         /*
 224          * Search for the first aliased symbol. Aliased
 225          * symbols are symbols with the same address.
 226          */
 227         while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
 228                 --low;
 229
 230         symbol_start = kallsyms_sym_address(low);
 231
 232         /* Search for next non-aliased symbol. */
 233         for (i = low + 1; i < kallsyms_num_syms; i++) {
 234                 if (kallsyms_sym_address(i) > symbol_start) {
 235                         symbol_end = kallsyms_sym_address(i);
 236                         break;
 237                 }
 238         }
 239
 240         /* If we found no next symbol, we use the end of the section. */
 241         if (!symbol_end) {
 242                 if (is_kernel_inittext(addr))
 243                         symbol_end = (unsigned long)_einittext;
 244                 else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
 245                         symbol_end = (unsigned long)_end;
 246                 else
 247                         symbol_end = (unsigned long)_etext;
 248         }
 249
 250         if (symbolsize)
 251                 *symbolsize = symbol_end - symbol_start;
 252         if (offset)
 253                 *offset = addr - symbol_start;
 254
 255         return low;
 256 }
 257
 258 /*
 259  * Lookup an address but don't bother to find any names.
 260  */
 261 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
 262                                 unsigned long *offset)
 263 {
 264         char namebuf[KSYM_NAME_LEN];
 265
 266         if (is_ksym_addr(addr))
 267                 return !!get_symbol_pos(addr, symbolsize, offset);
 268         return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
 269                !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
 270 }
 271
 272 /*
 273  * Lookup an address
 274  * - modname is set to NULL if it's in the kernel.
 275  * - We guarantee that the returned name is valid until we reschedule even if.
 276  *   It resides in a module.
 277  * - We also guarantee that modname will be valid until rescheduled.
 278  */
 279 const char *kallsyms_lookup(unsigned long addr,
 280                             unsigned long *symbolsize,
 281                             unsigned long *offset,
 282                             char **modname, char *namebuf)
 283 {
 284         const char *ret;
 285
 286         namebuf[KSYM_NAME_LEN - 1] = 0;
 287         namebuf[0] = 0;
 288
 289         if (is_ksym_addr(addr)) {
 290                 unsigned long pos;
 291
 292                 pos = get_symbol_pos(addr, symbolsize, offset);
 293                 /* Grab name */
 294                 kallsyms_expand_symbol(get_symbol_offset(pos),
 295                                        namebuf, KSYM_NAME_LEN);
 296                 if (modname)
 297                         *modname = NULL;
 298                 return namebuf;
 299         }
 300
 301         /* See if it's in a module or a BPF JITed image. */
 302         ret = module_address_lookup(addr, symbolsize, offset,
 303                                     modname, namebuf);
 304         if (!ret)
 305                 ret = bpf_address_lookup(addr, symbolsize,
 306                                          offset, modname, namebuf);
 307
 308         if (!ret)
 309                 ret = ftrace_mod_address_lookup(addr, symbolsize,
 310                                                 offset, modname, namebuf);
 311         return ret;
 312 }
 313
 314 int lookup_symbol_name(unsigned long addr, char *symname)
 315 {
 316         symname[0] = '\0';
 317         symname[KSYM_NAME_LEN - 1] = '\0';
 318
 319         if (is_ksym_addr(addr)) {
 320                 unsigned long pos;
 321
 322                 pos = get_symbol_pos(addr, NULL, NULL);
 323                 /* Grab name */
 324                 kallsyms_expand_symbol(get_symbol_offset(pos),
 325                                        symname, KSYM_NAME_LEN);
 326                 return 0;
 327         }
 328         /* See if it's in a module. */
 329         return lookup_module_symbol_name(addr, symname);
 330 }
 331
 332 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 333                         unsigned long *offset, char *modname, char *name)
 334 {
 335         name[0] = '\0';
 336         name[KSYM_NAME_LEN - 1] = '\0';
 337
 338         if (is_ksym_addr(addr)) {
 339                 unsigned long pos;
 340
 341                 pos = get_symbol_pos(addr, size, offset);
 342                 /* Grab name */
 343                 kallsyms_expand_symbol(get_symbol_offset(pos),
 344                                        name, KSYM_NAME_LEN);
 345                 modname[0] = '\0';
 346                 return 0;
 347         }
 348         /* See if it's in a module. */
 349         return lookup_module_symbol_attrs(addr, size, offset, modname, name);
 350 }
 351
 352 /* Look up a kernel symbol and return it in a text buffer. */
 353 static int __sprint_symbol(char *buffer, unsigned long address,
 354                            int symbol_offset, int add_offset)
 355 {
 356         char *modname;
 357         const char *name;
 358         unsigned long offset, size;
 359         int len;
 360
 361         address += symbol_offset;
 362         name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
 363         if (!name)
 364                 return sprintf(buffer, "0x%lx", address - symbol_offset);
 365
 366         if (name != buffer)
 367                 strcpy(buffer, name);
 368         len = strlen(buffer);
 369         offset -= symbol_offset;
 370
 371         if (add_offset)
 372                 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
 373
 374         if (modname)
 375                 len += sprintf(buffer + len, " [%s]", modname);
 376
 377         return len;
 378 }
 379
 380 /**
 381  * sprint_symbol - Look up a kernel symbol and return it in a text buffer
 382  * @buffer: buffer to be stored
 383  * @address: address to lookup
 384  *
 385  * This function looks up a kernel symbol with @address and stores its name,
 386  * offset, size and module name to @buffer if possible. If no symbol was found,
 387  * just saves its @address as is.
 388  *
 389  * This function returns the number of bytes stored in @buffer.
 390  */
 391 int sprint_symbol(char *buffer, unsigned long address)
 392 {
 393         return __sprint_symbol(buffer, address, 0, 1);
 394 }
 395 EXPORT_SYMBOL_GPL(sprint_symbol);
 396
 397 /**
 398  * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
 399  * @buffer: buffer to be stored
 400  * @address: address to lookup
 401  *
 402  * This function looks up a kernel symbol with @address and stores its name
 403  * and module name to @buffer if possible. If no symbol was found, just saves
 404  * its @address as is.
 405  *
 406  * This function returns the number of bytes stored in @buffer.
 407  */
 408 int sprint_symbol_no_offset(char *buffer, unsigned long address)
 409 {
 410         return __sprint_symbol(buffer, address, 0, 0);
 411 }
 412 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
 413
 414 /**
 415  * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
 416  * @buffer: buffer to be stored
 417  * @address: address to lookup
 418  *
 419  * This function is for stack backtrace and does the same thing as
 420  * sprint_symbol() but with modified/decreased @address. If there is a
 421  * tail-call to the function marked "noreturn", gcc optimized out code after
 422  * the call so that the stack-saved return address could point outside of the
 423  * caller. This function ensures that kallsyms will find the original caller
 424  * by decreasing @address.
 425  *
 426  * This function returns the number of bytes stored in @buffer.
 427  */
 428 int sprint_backtrace(char *buffer, unsigned long address)
 429 {
 430         return __sprint_symbol(buffer, address, -1, 1);
 431 }
 432
 433 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 434 struct kallsym_iter {
 435         loff_t pos;
 436         loff_t pos_arch_end;
 437         loff_t pos_mod_end;
 438         loff_t pos_ftrace_mod_end;
 439         unsigned long value;
 440         unsigned int nameoff; /* If iterating in core kernel symbols. */
 441         char type;
 442         char name[KSYM_NAME_LEN];
 443         char module_name[MODULE_NAME_LEN];
 444         int exported;
 445         int show_value;
 446 };
 447
 448 int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
 449                             char *type, char *name)
 450 {
 451         return -EINVAL;
 452 }
 453
 454 static int get_ksymbol_arch(struct kallsym_iter *iter)
 455 {
 456         int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
 457                                    &iter->value, &iter->type,
 458                                    iter->name);
 459
 460         if (ret < 0) {
 461                 iter->pos_arch_end = iter->pos;
 462                 return 0;
 463         }
 464
 465         return 1;
 466 }
 467
 468 static int get_ksymbol_mod(struct kallsym_iter *iter)
 469 {
 470         int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
 471                                      &iter->value, &iter->type,
 472                                      iter->name, iter->module_name,
 473                                      &iter->exported);
 474         if (ret < 0) {
 475                 iter->pos_mod_end = iter->pos;
 476                 return 0;
 477         }
 478
 479         return 1;
 480 }
 481
 482 static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
 483 {
 484         int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
 485                                          &iter->value, &iter->type,
 486                                          iter->name, iter->module_name,
 487                                          &iter->exported);
 488         if (ret < 0) {
 489                 iter->pos_ftrace_mod_end = iter->pos;
 490                 return 0;
 491         }
 492
 493         return 1;
 494 }
 495
 496 static int get_ksymbol_bpf(struct kallsym_iter *iter)
 497 {
 498         strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
 499         iter->exported = 0;
 500         return bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
 501                                &iter->value, &iter->type,
 502                                iter->name) < 0 ? 0 : 1;
 503 }
 504
 505 /* Returns space to next name. */
 506 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 507 {
 508         unsigned off = iter->nameoff;
 509
 510         iter->module_name[0] = '\0';
 511         iter->value = kallsyms_sym_address(iter->pos);
 512
 513         iter->type = kallsyms_get_symbol_type(off);
 514
 515         off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
 516
 517         return off - iter->nameoff;
 518 }
 519
 520 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 521 {
 522         iter->name[0] = '\0';
 523         iter->nameoff = get_symbol_offset(new_pos);
 524         iter->pos = new_pos;
 525         if (new_pos == 0) {
 526                 iter->pos_arch_end = 0;
 527                 iter->pos_mod_end = 0;
 528                 iter->pos_ftrace_mod_end = 0;
 529         }
 530 }
 531
 532 /*
 533  * The end position (last + 1) of each additional kallsyms section is recorded
 534  * in iter->pos_..._end as each section is added, and so can be used to
 535  * determine which get_ksymbol_...() function to call next.
 536  */
 537 static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
 538 {
 539         iter->pos = pos;
 540
 541         if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
 542             get_ksymbol_arch(iter))
 543                 return 1;
 544
 545         if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
 546             get_ksymbol_mod(iter))
 547                 return 1;
 548
 549         if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
 550             get_ksymbol_ftrace_mod(iter))
 551                 return 1;
 552
 553         return get_ksymbol_bpf(iter);
 554 }
 555
 556 /* Returns false if pos at or past end of file. */
 557 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 558 {
 559         /* Module symbols can be accessed randomly. */
 560         if (pos >= kallsyms_num_syms)
 561                 return update_iter_mod(iter, pos);
 562
 563         /* If we're not on the desired position, reset to new position. */
 564         if (pos != iter->pos)
 565                 reset_iter(iter, pos);
 566
 567         iter->nameoff += get_ksymbol_core(iter);
 568         iter->pos++;
 569
 570         return 1;
 571 }
 572
 573 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 574 {
 575         (*pos)++;
 576
 577         if (!update_iter(m->private, *pos))
 578                 return NULL;
 579         return p;
 580 }
 581
 582 static void *s_start(struct seq_file *m, loff_t *pos)
 583 {
 584         if (!update_iter(m->private, *pos))
 585                 return NULL;
 586         return m->private;
 587 }
 588
 589 static void s_stop(struct seq_file *m, void *p)
 590 {
 591 }
 592
 593 static int s_show(struct seq_file *m, void *p)
 594 {
 595         void *value;
 596         struct kallsym_iter *iter = m->private;
 597
 598         /* Some debugging symbols have no name.  Ignore them. */
 599         if (!iter->name[0])
 600                 return 0;
 601
 602         value = iter->show_value ? (void *)iter->value : NULL;
 603
 604         if (iter->module_name[0]) {
 605                 char type;
 606
 607                 /*
 608                  * Label it "global" if it is exported,
 609                  * "local" if not exported.
 610                  */
 611                 type = iter->exported ? toupper(iter->type) :
 612                                         tolower(iter->type);
 613                 seq_printf(m, "%px %c %s\t[%s]\n", value,
 614                            type, iter->name, iter->module_name);
 615         } else
 616                 seq_printf(m, "%px %c %s\n", value,
 617                            iter->type, iter->name);
 618         return 0;
 619 }
 620
 621 static const struct seq_operations kallsyms_op = {
 622         .start = s_start,
 623         .next = s_next,
 624         .stop = s_stop,
 625         .show = s_show
 626 };
 627
 628 static inline int kallsyms_for_perf(void)
 629 {
 630 #ifdef CONFIG_PERF_EVENTS
 631         extern int sysctl_perf_event_paranoid;
 632         if (sysctl_perf_event_paranoid <= 1)
 633                 return 1;
 634 #endif
 635         return 0;
 636 }
 637
 638 /*
 639  * We show kallsyms information even to normal users if we've enabled
 640  * kernel profiling and are explicitly not paranoid (so kptr_restrict
 641  * is clear, and sysctl_perf_event_paranoid isn't set).
 642  *
 643  * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
 644  * block even that).
 645  */
 646 int kallsyms_show_value(void)
 647 {
 648         switch (kptr_restrict) {
 649         case 0:
 650                 if (kallsyms_for_perf())
 651                         return 1;
 652         /* fallthrough */
 653         case 1:
 654                 if (has_capability_noaudit(current, CAP_SYSLOG))
 655                         return 1;
 656         /* fallthrough */
 657         default:
 658                 return 0;
 659         }
 660 }
 661
 662 static int kallsyms_open(struct inode *inode, struct file *file)
 663 {
 664         /*
 665          * We keep iterator in m->private, since normal case is to
 666          * s_start from where we left off, so we avoid doing
 667          * using get_symbol_offset for every symbol.
 668          */
 669         struct kallsym_iter *iter;
 670         iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
 671         if (!iter)
 672                 return -ENOMEM;
 673         reset_iter(iter, 0);
 674
 675         iter->show_value = kallsyms_show_value();
 676         return 0;
 677 }
 678
 679 #ifdef  CONFIG_KGDB_KDB
 680 const char *kdb_walk_kallsyms(loff_t *pos)
 681 {
 682         static struct kallsym_iter kdb_walk_kallsyms_iter;
 683         if (*pos == 0) {
 684                 memset(&kdb_walk_kallsyms_iter, 0,
 685                        sizeof(kdb_walk_kallsyms_iter));
 686                 reset_iter(&kdb_walk_kallsyms_iter, 0);
 687         }
 688         while (1) {
 689                 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
 690                         return NULL;
 691                 ++*pos;
 692                 /* Some debugging symbols have no name.  Ignore them. */
 693                 if (kdb_walk_kallsyms_iter.name[0])
 694                         return kdb_walk_kallsyms_iter.name;
 695         }
 696 }
 697 #endif  /* CONFIG_KGDB_KDB */
 698
 699 static const struct file_operations kallsyms_operations = {
 700         .open = kallsyms_open,
 701         .read = seq_read,
 702         .llseek = seq_lseek,
 703         .release = seq_release_private,
 704 };
 705
 706 static int __init kallsyms_init(void)
 707 {
 708         proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
 709         return 0;
 710 }
 711 device_initcall(kallsyms_init);