kernel/kallsyms.c

   1 /*
   2  * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
   3  *
   4  * Rewritten and vastly simplified by Rusty Russell for in-kernel
   5  * module loader:
   6  *   Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
   7  *
   8  * ChangeLog:
   9  *
  10  * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
  11  *      Changed the compression method from stem compression to "table lookup"
  12  *      compression (see scripts/kallsyms.c for a more complete description)
  13  */
  14 #include <linux/kallsyms.h>
  15 #include <linux/module.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/mm.h>
  24 #include <linux/ctype.h>
  25 #include <linux/slab.h>
  26
  27 #include <asm/sections.h>
  28
  29 #ifdef CONFIG_KALLSYMS_ALL
  30 #define all_var 1
  31 #else
  32 #define all_var 0
  33 #endif
  34
  35 /*
  36  * These will be re-linked against their real values
  37  * during the second link stage.
  38  */
  39 extern const unsigned long kallsyms_addresses[] __attribute__((weak));
  40 extern const u8 kallsyms_names[] __attribute__((weak));
  41
  42 /*
  43  * Tell the compiler that the count isn't in the small data section if the arch
  44  * has one (eg: FRV).
  45  */
  46 extern const unsigned long kallsyms_num_syms
  47 __attribute__((weak, section(".rodata")));
  48
  49 extern const u8 kallsyms_token_table[] __attribute__((weak));
  50 extern const u16 kallsyms_token_index[] __attribute__((weak));
  51
  52 extern const unsigned long kallsyms_markers[] __attribute__((weak));
  53
  54 static inline int is_kernel_inittext(unsigned long addr)
  55 {
  56         if (addr >= (unsigned long)_sinittext
  57             && addr <= (unsigned long)_einittext)
  58                 return 1;
  59         return 0;
  60 }
  61
  62 static inline int is_kernel_text(unsigned long addr)
  63 {
  64         if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
  65             arch_is_kernel_text(addr))
  66                 return 1;
  67         return in_gate_area_no_task(addr);
  68 }
  69
  70 static inline int is_kernel(unsigned long addr)
  71 {
  72         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
  73                 return 1;
  74         return in_gate_area_no_task(addr);
  75 }
  76
  77 static int is_ksym_addr(unsigned long addr)
  78 {
  79         if (all_var)
  80                 return is_kernel(addr);
  81
  82         return is_kernel_text(addr) || is_kernel_inittext(addr);
  83 }
  84
  85 /*
  86  * Expand a compressed symbol data into the resulting uncompressed string,
  87  * given the offset to where the symbol is in the compressed stream.
  88  */
  89 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
  90 {
  91         int len, skipped_first = 0;
  92         const u8 *tptr, *data;
  93
  94         /* Get the compressed symbol length from the first symbol byte. */
  95         data = &kallsyms_names[off];
  96         len = *data;
  97         data++;
  98
  99         /*
 100          * Update the offset to return the offset for the next symbol on
 101          * the compressed stream.
 102          */
 103         off += len + 1;
 104
 105         /*
 106          * For every byte on the compressed symbol data, copy the table
 107          * entry for that byte.
 108          */
 109         while (len) {
 110                 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
 111                 data++;
 112                 len--;
 113
 114                 while (*tptr) {
 115                         if (skipped_first) {
 116                                 *result = *tptr;
 117                                 result++;
 118                         } else
 119                                 skipped_first = 1;
 120                         tptr++;
 121                 }
 122         }
 123
 124         *result = '\0';
 125
 126         /* Return to offset to the next symbol. */
 127         return off;
 128 }
 129
 130 /*
 131  * Get symbol type information. This is encoded as a single char at the
 132  * beginning of the symbol name.
 133  */
 134 static char kallsyms_get_symbol_type(unsigned int off)
 135 {
 136         /*
 137          * Get just the first code, look it up in the token table,
 138          * and return the first char from this token.
 139          */
 140         return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
 141 }
 142
 143
 144 /*
 145  * Find the offset on the compressed stream given and index in the
 146  * kallsyms array.
 147  */
 148 static unsigned int get_symbol_offset(unsigned long pos)
 149 {
 150         const u8 *name;
 151         int i;
 152
 153         /*
 154          * Use the closest marker we have. We have markers every 256 positions,
 155          * so that should be close enough.
 156          */
 157         name = &kallsyms_names[kallsyms_markers[pos >> 8]];
 158
 159         /*
 160          * Sequentially scan all the symbols up to the point we're searching
 161          * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
 162          * so we just need to add the len to the current pointer for every
 163          * symbol we wish to skip.
 164          */
 165         for (i = 0; i < (pos & 0xFF); i++)
 166                 name = name + (*name) + 1;
 167
 168         return name - kallsyms_names;
 169 }
 170
 171 /* Lookup the address for this symbol. Returns 0 if not found. */
 172 unsigned long kallsyms_lookup_name(const char *name)
 173 {
 174         char namebuf[KSYM_NAME_LEN];
 175         unsigned long i;
 176         unsigned int off;
 177
 178         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 179                 off = kallsyms_expand_symbol(off, namebuf);
 180
 181                 if (strcmp(namebuf, name) == 0)
 182                         return kallsyms_addresses[i];
 183         }
 184         return module_kallsyms_lookup_name(name);
 185 }
 186 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
 187
 188 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 189                                       unsigned long),
 190                             void *data)
 191 {
 192         char namebuf[KSYM_NAME_LEN];
 193         unsigned long i;
 194         unsigned int off;
 195         int ret;
 196
 197         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 198                 off = kallsyms_expand_symbol(off, namebuf);
 199                 ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
 200                 if (ret != 0)
 201                         return ret;
 202         }
 203         return module_kallsyms_on_each_symbol(fn, data);
 204 }
 205 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
 206
 207 static unsigned long get_symbol_pos(unsigned long addr,
 208                                     unsigned long *symbolsize,
 209                                     unsigned long *offset)
 210 {
 211         unsigned long symbol_start = 0, symbol_end = 0;
 212         unsigned long i, low, high, mid;
 213
 214         /* This kernel should never had been booted. */
 215         BUG_ON(!kallsyms_addresses);
 216
 217         /* Do a binary search on the sorted kallsyms_addresses array. */
 218         low = 0;
 219         high = kallsyms_num_syms;
 220
 221         while (high - low > 1) {
 222                 mid = low + (high - low) / 2;
 223                 if (kallsyms_addresses[mid] <= addr)
 224                         low = mid;
 225                 else
 226                         high = mid;
 227         }
 228
 229         /*
 230          * Search for the first aliased symbol. Aliased
 231          * symbols are symbols with the same address.
 232          */
 233         while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
 234                 --low;
 235
 236         symbol_start = kallsyms_addresses[low];
 237
 238         /* Search for next non-aliased symbol. */
 239         for (i = low + 1; i < kallsyms_num_syms; i++) {
 240                 if (kallsyms_addresses[i] > symbol_start) {
 241                         symbol_end = kallsyms_addresses[i];
 242                         break;
 243                 }
 244         }
 245
 246         /* If we found no next symbol, we use the end of the section. */
 247         if (!symbol_end) {
 248                 if (is_kernel_inittext(addr))
 249                         symbol_end = (unsigned long)_einittext;
 250                 else if (all_var)
 251                         symbol_end = (unsigned long)_end;
 252                 else
 253                         symbol_end = (unsigned long)_etext;
 254         }
 255
 256         if (symbolsize)
 257                 *symbolsize = symbol_end - symbol_start;
 258         if (offset)
 259                 *offset = addr - symbol_start;
 260
 261         return low;
 262 }
 263
 264 /*
 265  * Lookup an address but don't bother to find any names.
 266  */
 267 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
 268                                 unsigned long *offset)
 269 {
 270         char namebuf[KSYM_NAME_LEN];
 271         if (is_ksym_addr(addr))
 272                 return !!get_symbol_pos(addr, symbolsize, offset);
 273
 274         return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
 275 }
 276
 277 /*
 278  * Lookup an address
 279  * - modname is set to NULL if it's in the kernel.
 280  * - We guarantee that the returned name is valid until we reschedule even if.
 281  *   It resides in a module.
 282  * - We also guarantee that modname will be valid until rescheduled.
 283  */
 284 const char *kallsyms_lookup(unsigned long addr,
 285                             unsigned long *symbolsize,
 286                             unsigned long *offset,
 287                             char **modname, char *namebuf)
 288 {
 289         namebuf[KSYM_NAME_LEN - 1] = 0;
 290         namebuf[0] = 0;
 291
 292         if (is_ksym_addr(addr)) {
 293                 unsigned long pos;
 294
 295                 pos = get_symbol_pos(addr, symbolsize, offset);
 296                 /* Grab name */
 297                 kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
 298                 if (modname)
 299                         *modname = NULL;
 300                 return namebuf;
 301         }
 302
 303         /* See if it's in a module. */
 304         return module_address_lookup(addr, symbolsize, offset, modname,
 305                                      namebuf);
 306 }
 307
 308 int lookup_symbol_name(unsigned long addr, char *symname)
 309 {
 310         symname[0] = '\0';
 311         symname[KSYM_NAME_LEN - 1] = '\0';
 312
 313         if (is_ksym_addr(addr)) {
 314                 unsigned long pos;
 315
 316                 pos = get_symbol_pos(addr, NULL, NULL);
 317                 /* Grab name */
 318                 kallsyms_expand_symbol(get_symbol_offset(pos), symname);
 319                 return 0;
 320         }
 321         /* See if it's in a module. */
 322         return lookup_module_symbol_name(addr, symname);
 323 }
 324
 325 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 326                         unsigned long *offset, char *modname, char *name)
 327 {
 328         name[0] = '\0';
 329         name[KSYM_NAME_LEN - 1] = '\0';
 330
 331         if (is_ksym_addr(addr)) {
 332                 unsigned long pos;
 333
 334                 pos = get_symbol_pos(addr, size, offset);
 335                 /* Grab name */
 336                 kallsyms_expand_symbol(get_symbol_offset(pos), name);
 337                 modname[0] = '\0';
 338                 return 0;
 339         }
 340         /* See if it's in a module. */
 341         return lookup_module_symbol_attrs(addr, size, offset, modname, name);
 342 }
 343
 344 /* Look up a kernel symbol and return it in a text buffer. */
 345 int sprint_symbol(char *buffer, unsigned long address)
 346 {
 347         char *modname;
 348         const char *name;
 349         unsigned long offset, size;
 350         int len;
 351
 352         name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
 353         if (!name)
 354                 return sprintf(buffer, "0x%lx", address);
 355
 356         if (name != buffer)
 357                 strcpy(buffer, name);
 358         len = strlen(buffer);
 359         buffer += len;
 360
 361         if (modname)
 362                 len += sprintf(buffer, "+%#lx/%#lx [%s]",
 363                                                 offset, size, modname);
 364         else
 365                 len += sprintf(buffer, "+%#lx/%#lx", offset, size);
 366
 367         return len;
 368 }
 369 EXPORT_SYMBOL_GPL(sprint_symbol);
 370
 371 /* Look up a kernel symbol and print it to the kernel messages. */
 372 void __print_symbol(const char *fmt, unsigned long address)
 373 {
 374         char buffer[KSYM_SYMBOL_LEN];
 375
 376         sprint_symbol(buffer, address);
 377
 378         printk(fmt, buffer);
 379 }
 380 EXPORT_SYMBOL(__print_symbol);
 381
 382 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 383 struct kallsym_iter {
 384         loff_t pos;
 385         unsigned long value;
 386         unsigned int nameoff; /* If iterating in core kernel symbols. */
 387         char type;
 388         char name[KSYM_NAME_LEN];
 389         char module_name[MODULE_NAME_LEN];
 390         int exported;
 391 };
 392
 393 static int get_ksymbol_mod(struct kallsym_iter *iter)
 394 {
 395         if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
 396                                 &iter->type, iter->name, iter->module_name,
 397                                 &iter->exported) < 0)
 398                 return 0;
 399         return 1;
 400 }
 401
 402 /* Returns space to next name. */
 403 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 404 {
 405         unsigned off = iter->nameoff;
 406
 407         iter->module_name[0] = '\0';
 408         iter->value = kallsyms_addresses[iter->pos];
 409
 410         iter->type = kallsyms_get_symbol_type(off);
 411
 412         off = kallsyms_expand_symbol(off, iter->name);
 413
 414         return off - iter->nameoff;
 415 }
 416
 417 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 418 {
 419         iter->name[0] = '\0';
 420         iter->nameoff = get_symbol_offset(new_pos);
 421         iter->pos = new_pos;
 422 }
 423
 424 /* Returns false if pos at or past end of file. */
 425 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 426 {
 427         /* Module symbols can be accessed randomly. */
 428         if (pos >= kallsyms_num_syms) {
 429                 iter->pos = pos;
 430                 return get_ksymbol_mod(iter);
 431         }
 432
 433         /* If we're not on the desired position, reset to new position. */
 434         if (pos != iter->pos)
 435                 reset_iter(iter, pos);
 436
 437         iter->nameoff += get_ksymbol_core(iter);
 438         iter->pos++;
 439
 440         return 1;
 441 }
 442
 443 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 444 {
 445         (*pos)++;
 446
 447         if (!update_iter(m->private, *pos))
 448                 return NULL;
 449         return p;
 450 }
 451
 452 static void *s_start(struct seq_file *m, loff_t *pos)
 453 {
 454         if (!update_iter(m->private, *pos))
 455                 return NULL;
 456         return m->private;
 457 }
 458
 459 static void s_stop(struct seq_file *m, void *p)
 460 {
 461 }
 462
 463 static int s_show(struct seq_file *m, void *p)
 464 {
 465         struct kallsym_iter *iter = m->private;
 466
 467         /* Some debugging symbols have no name.  Ignore them. */
 468         if (!iter->name[0])
 469                 return 0;
 470
 471         if (iter->module_name[0]) {
 472                 char type;
 473
 474                 /*
 475                  * Label it "global" if it is exported,
 476                  * "local" if not exported.
 477                  */
 478                 type = iter->exported ? toupper(iter->type) :
 479                                         tolower(iter->type);
 480                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 481                            (int)(2 * sizeof(void *)),
 482                            iter->value, type, iter->name, iter->module_name);
 483         } else
 484                 seq_printf(m, "%0*lx %c %s\n",
 485                            (int)(2 * sizeof(void *)),
 486                            iter->value, iter->type, iter->name);
 487         return 0;
 488 }
 489
 490 static const struct seq_operations kallsyms_op = {
 491         .start = s_start,
 492         .next = s_next,
 493         .stop = s_stop,
 494         .show = s_show
 495 };
 496
 497 static int kallsyms_open(struct inode *inode, struct file *file)
 498 {
 499         /*
 500          * We keep iterator in m->private, since normal case is to
 501          * s_start from where we left off, so we avoid doing
 502          * using get_symbol_offset for every symbol.
 503          */
 504         struct kallsym_iter *iter;
 505         int ret;
 506
 507         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 508         if (!iter)
 509                 return -ENOMEM;
 510         reset_iter(iter, 0);
 511
 512         ret = seq_open(file, &kallsyms_op);
 513         if (ret == 0)
 514                 ((struct seq_file *)file->private_data)->private = iter;
 515         else
 516                 kfree(iter);
 517         return ret;
 518 }
 519
 520 #ifdef  CONFIG_KGDB_KDB
 521 const char *kdb_walk_kallsyms(loff_t *pos)
 522 {
 523         static struct kallsym_iter kdb_walk_kallsyms_iter;
 524         if (*pos == 0) {
 525                 memset(&kdb_walk_kallsyms_iter, 0,
 526                        sizeof(kdb_walk_kallsyms_iter));
 527                 reset_iter(&kdb_walk_kallsyms_iter, 0);
 528         }
 529         while (1) {
 530                 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
 531                         return NULL;
 532                 ++*pos;
 533                 /* Some debugging symbols have no name.  Ignore them. */
 534                 if (kdb_walk_kallsyms_iter.name[0])
 535                         return kdb_walk_kallsyms_iter.name;
 536         }
 537 }
 538 #endif  /* CONFIG_KGDB_KDB */
 539
 540 static const struct file_operations kallsyms_operations = {
 541         .open = kallsyms_open,
 542         .read = seq_read,
 543         .llseek = seq_lseek,
 544         .release = seq_release_private,
 545 };
 546
 547 static int __init kallsyms_init(void)
 548 {
 549         proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
 550         return 0;
 551 }
 552 device_initcall(kallsyms_init);