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_mm(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_mm(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  * if uncompressed string is too long (>= maxlen), it will be truncated,
  88  * given the offset to where the symbol is in the compressed stream.
  89  */
  90 static unsigned int kallsyms_expand_symbol(unsigned int off,
  91                                            char *result, size_t maxlen)
  92 {
  93         int len, skipped_first = 0;
  94         const u8 *tptr, *data;
  95
  96         /* Get the compressed symbol length from the first symbol byte. */
  97         data = &kallsyms_names[off];
  98         len = *data;
  99         data++;
 100
 101         /*
 102          * Update the offset to return the offset for the next symbol on
 103          * the compressed stream.
 104          */
 105         off += len + 1;
 106
 107         /*
 108          * For every byte on the compressed symbol data, copy the table
 109          * entry for that byte.
 110          */
 111         while (len) {
 112                 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
 113                 data++;
 114                 len--;
 115
 116                 while (*tptr) {
 117                         if (skipped_first) {
 118                                 if (maxlen <= 1)
 119                                         goto tail;
 120                                 *result = *tptr;
 121                                 result++;
 122                                 maxlen--;
 123                         } else
 124                                 skipped_first = 1;
 125                         tptr++;
 126                 }
 127         }
 128
 129 tail:
 130         if (maxlen)
 131                 *result = '\0';
 132
 133         /* Return to offset to the next symbol. */
 134         return off;
 135 }
 136
 137 /*
 138  * Get symbol type information. This is encoded as a single char at the
 139  * beginning of the symbol name.
 140  */
 141 static char kallsyms_get_symbol_type(unsigned int off)
 142 {
 143         /*
 144          * Get just the first code, look it up in the token table,
 145          * and return the first char from this token.
 146          */
 147         return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
 148 }
 149
 150
 151 /*
 152  * Find the offset on the compressed stream given and index in the
 153  * kallsyms array.
 154  */
 155 static unsigned int get_symbol_offset(unsigned long pos)
 156 {
 157         const u8 *name;
 158         int i;
 159
 160         /*
 161          * Use the closest marker we have. We have markers every 256 positions,
 162          * so that should be close enough.
 163          */
 164         name = &kallsyms_names[kallsyms_markers[pos >> 8]];
 165
 166         /*
 167          * Sequentially scan all the symbols up to the point we're searching
 168          * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
 169          * so we just need to add the len to the current pointer for every
 170          * symbol we wish to skip.
 171          */
 172         for (i = 0; i < (pos & 0xFF); i++)
 173                 name = name + (*name) + 1;
 174
 175         return name - kallsyms_names;
 176 }
 177
 178 /* Lookup the address for this symbol. Returns 0 if not found. */
 179 unsigned long kallsyms_lookup_name(const char *name)
 180 {
 181         char namebuf[KSYM_NAME_LEN];
 182         unsigned long i;
 183         unsigned int off;
 184
 185         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 186                 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 187
 188                 if (strcmp(namebuf, name) == 0)
 189                         return kallsyms_addresses[i];
 190         }
 191         return module_kallsyms_lookup_name(name);
 192 }
 193 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
 194
 195 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 196                                       unsigned long),
 197                             void *data)
 198 {
 199         char namebuf[KSYM_NAME_LEN];
 200         unsigned long i;
 201         unsigned int off;
 202         int ret;
 203
 204         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 205                 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 206                 ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
 207                 if (ret != 0)
 208                         return ret;
 209         }
 210         return module_kallsyms_on_each_symbol(fn, data);
 211 }
 212 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
 213
 214 static unsigned long get_symbol_pos(unsigned long addr,
 215                                     unsigned long *symbolsize,
 216                                     unsigned long *offset)
 217 {
 218         unsigned long symbol_start = 0, symbol_end = 0;
 219         unsigned long i, low, high, mid;
 220
 221         /* This kernel should never had been booted. */
 222         BUG_ON(!kallsyms_addresses);
 223
 224         /* Do a binary search on the sorted kallsyms_addresses array. */
 225         low = 0;
 226         high = kallsyms_num_syms;
 227
 228         while (high - low > 1) {
 229                 mid = low + (high - low) / 2;
 230                 if (kallsyms_addresses[mid] <= addr)
 231                         low = mid;
 232                 else
 233                         high = mid;
 234         }
 235
 236         /*
 237          * Search for the first aliased symbol. Aliased
 238          * symbols are symbols with the same address.
 239          */
 240         while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
 241                 --low;
 242
 243         symbol_start = kallsyms_addresses[low];
 244
 245         /* Search for next non-aliased symbol. */
 246         for (i = low + 1; i < kallsyms_num_syms; i++) {
 247                 if (kallsyms_addresses[i] > symbol_start) {
 248                         symbol_end = kallsyms_addresses[i];
 249                         break;
 250                 }
 251         }
 252
 253         /* If we found no next symbol, we use the end of the section. */
 254         if (!symbol_end) {
 255                 if (is_kernel_inittext(addr))
 256                         symbol_end = (unsigned long)_einittext;
 257                 else if (all_var)
 258                         symbol_end = (unsigned long)_end;
 259                 else
 260                         symbol_end = (unsigned long)_etext;
 261         }
 262
 263         if (symbolsize)
 264                 *symbolsize = symbol_end - symbol_start;
 265         if (offset)
 266                 *offset = addr - symbol_start;
 267
 268         return low;
 269 }
 270
 271 /*
 272  * Lookup an address but don't bother to find any names.
 273  */
 274 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
 275                                 unsigned long *offset)
 276 {
 277         char namebuf[KSYM_NAME_LEN];
 278         if (is_ksym_addr(addr))
 279                 return !!get_symbol_pos(addr, symbolsize, offset);
 280
 281         return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
 282 }
 283
 284 /*
 285  * Lookup an address
 286  * - modname is set to NULL if it's in the kernel.
 287  * - We guarantee that the returned name is valid until we reschedule even if.
 288  *   It resides in a module.
 289  * - We also guarantee that modname will be valid until rescheduled.
 290  */
 291 const char *kallsyms_lookup(unsigned long addr,
 292                             unsigned long *symbolsize,
 293                             unsigned long *offset,
 294                             char **modname, char *namebuf)
 295 {
 296         namebuf[KSYM_NAME_LEN - 1] = 0;
 297         namebuf[0] = 0;
 298
 299         if (is_ksym_addr(addr)) {
 300                 unsigned long pos;
 301
 302                 pos = get_symbol_pos(addr, symbolsize, offset);
 303                 /* Grab name */
 304                 kallsyms_expand_symbol(get_symbol_offset(pos),
 305                                        namebuf, KSYM_NAME_LEN);
 306                 if (modname)
 307                         *modname = NULL;
 308                 return namebuf;
 309         }
 310
 311         /* See if it's in a module. */
 312         return module_address_lookup(addr, symbolsize, offset, modname,
 313                                      namebuf);
 314 }
 315
 316 int lookup_symbol_name(unsigned long addr, char *symname)
 317 {
 318         symname[0] = '\0';
 319         symname[KSYM_NAME_LEN - 1] = '\0';
 320
 321         if (is_ksym_addr(addr)) {
 322                 unsigned long pos;
 323
 324                 pos = get_symbol_pos(addr, NULL, NULL);
 325                 /* Grab name */
 326                 kallsyms_expand_symbol(get_symbol_offset(pos),
 327                                        symname, KSYM_NAME_LEN);
 328                 return 0;
 329         }
 330         /* See if it's in a module. */
 331         return lookup_module_symbol_name(addr, symname);
 332 }
 333
 334 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 335                         unsigned long *offset, char *modname, char *name)
 336 {
 337         name[0] = '\0';
 338         name[KSYM_NAME_LEN - 1] = '\0';
 339
 340         if (is_ksym_addr(addr)) {
 341                 unsigned long pos;
 342
 343                 pos = get_symbol_pos(addr, size, offset);
 344                 /* Grab name */
 345                 kallsyms_expand_symbol(get_symbol_offset(pos),
 346                                        name, KSYM_NAME_LEN);
 347                 modname[0] = '\0';
 348                 return 0;
 349         }
 350         /* See if it's in a module. */
 351         return lookup_module_symbol_attrs(addr, size, offset, modname, name);
 352 }
 353
 354 /* Look up a kernel symbol and return it in a text buffer. */
 355 static int __sprint_symbol(char *buffer, unsigned long address,
 356                            int symbol_offset, int add_offset)
 357 {
 358         char *modname;
 359         const char *name;
 360         unsigned long offset, size;
 361         int len;
 362
 363         address += symbol_offset;
 364         name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
 365         if (!name)
 366                 return sprintf(buffer, "0x%lx", address);
 367
 368         if (name != buffer)
 369                 strcpy(buffer, name);
 370         len = strlen(buffer);
 371         offset -= symbol_offset;
 372
 373         if (add_offset)
 374                 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
 375
 376         if (modname)
 377                 len += sprintf(buffer + len, " [%s]", modname);
 378
 379         return len;
 380 }
 381
 382 /**
 383  * sprint_symbol - Look up a kernel symbol and return it in a text buffer
 384  * @buffer: buffer to be stored
 385  * @address: address to lookup
 386  *
 387  * This function looks up a kernel symbol with @address and stores its name,
 388  * offset, size and module name to @buffer if possible. If no symbol was found,
 389  * just saves its @address as is.
 390  *
 391  * This function returns the number of bytes stored in @buffer.
 392  */
 393 int sprint_symbol(char *buffer, unsigned long address)
 394 {
 395         return __sprint_symbol(buffer, address, 0, 1);
 396 }
 397 EXPORT_SYMBOL_GPL(sprint_symbol);
 398
 399 /**
 400  * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
 401  * @buffer: buffer to be stored
 402  * @address: address to lookup
 403  *
 404  * This function looks up a kernel symbol with @address and stores its name
 405  * and module name to @buffer if possible. If no symbol was found, just saves
 406  * its @address as is.
 407  *
 408  * This function returns the number of bytes stored in @buffer.
 409  */
 410 int sprint_symbol_no_offset(char *buffer, unsigned long address)
 411 {
 412         return __sprint_symbol(buffer, address, 0, 0);
 413 }
 414 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
 415
 416 /**
 417  * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
 418  * @buffer: buffer to be stored
 419  * @address: address to lookup
 420  *
 421  * This function is for stack backtrace and does the same thing as
 422  * sprint_symbol() but with modified/decreased @address. If there is a
 423  * tail-call to the function marked "noreturn", gcc optimized out code after
 424  * the call so that the stack-saved return address could point outside of the
 425  * caller. This function ensures that kallsyms will find the original caller
 426  * by decreasing @address.
 427  *
 428  * This function returns the number of bytes stored in @buffer.
 429  */
 430 int sprint_backtrace(char *buffer, unsigned long address)
 431 {
 432         return __sprint_symbol(buffer, address, -1, 1);
 433 }
 434
 435 /* Look up a kernel symbol and print it to the kernel messages. */
 436 void __print_symbol(const char *fmt, unsigned long address)
 437 {
 438         char buffer[KSYM_SYMBOL_LEN];
 439
 440         sprint_symbol(buffer, address);
 441
 442         printk(fmt, buffer);
 443 }
 444 EXPORT_SYMBOL(__print_symbol);
 445
 446 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 447 struct kallsym_iter {
 448         loff_t pos;
 449         unsigned long value;
 450         unsigned int nameoff; /* If iterating in core kernel symbols. */
 451         char type;
 452         char name[KSYM_NAME_LEN];
 453         char module_name[MODULE_NAME_LEN];
 454         int exported;
 455 };
 456
 457 static int get_ksymbol_mod(struct kallsym_iter *iter)
 458 {
 459         if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
 460                                 &iter->type, iter->name, iter->module_name,
 461                                 &iter->exported) < 0)
 462                 return 0;
 463         return 1;
 464 }
 465
 466 /* Returns space to next name. */
 467 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 468 {
 469         unsigned off = iter->nameoff;
 470
 471         iter->module_name[0] = '\0';
 472         iter->value = kallsyms_addresses[iter->pos];
 473
 474         iter->type = kallsyms_get_symbol_type(off);
 475
 476         off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
 477
 478         return off - iter->nameoff;
 479 }
 480
 481 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 482 {
 483         iter->name[0] = '\0';
 484         iter->nameoff = get_symbol_offset(new_pos);
 485         iter->pos = new_pos;
 486 }
 487
 488 /* Returns false if pos at or past end of file. */
 489 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 490 {
 491         /* Module symbols can be accessed randomly. */
 492         if (pos >= kallsyms_num_syms) {
 493                 iter->pos = pos;
 494                 return get_ksymbol_mod(iter);
 495         }
 496
 497         /* If we're not on the desired position, reset to new position. */
 498         if (pos != iter->pos)
 499                 reset_iter(iter, pos);
 500
 501         iter->nameoff += get_ksymbol_core(iter);
 502         iter->pos++;
 503
 504         return 1;
 505 }
 506
 507 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 508 {
 509         (*pos)++;
 510
 511         if (!update_iter(m->private, *pos))
 512                 return NULL;
 513         return p;
 514 }
 515
 516 static void *s_start(struct seq_file *m, loff_t *pos)
 517 {
 518         if (!update_iter(m->private, *pos))
 519                 return NULL;
 520         return m->private;
 521 }
 522
 523 static void s_stop(struct seq_file *m, void *p)
 524 {
 525 }
 526
 527 static int s_show(struct seq_file *m, void *p)
 528 {
 529         struct kallsym_iter *iter = m->private;
 530
 531         /* Some debugging symbols have no name.  Ignore them. */
 532         if (!iter->name[0])
 533                 return 0;
 534
 535         if (iter->module_name[0]) {
 536                 char type;
 537
 538                 /*
 539                  * Label it "global" if it is exported,
 540                  * "local" if not exported.
 541                  */
 542                 type = iter->exported ? toupper(iter->type) :
 543                                         tolower(iter->type);
 544                 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
 545                            type, iter->name, iter->module_name);
 546         } else
 547                 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
 548                            iter->type, iter->name);
 549         return 0;
 550 }
 551
 552 static const struct seq_operations kallsyms_op = {
 553         .start = s_start,
 554         .next = s_next,
 555         .stop = s_stop,
 556         .show = s_show
 557 };
 558
 559 static int kallsyms_open(struct inode *inode, struct file *file)
 560 {
 561         /*
 562          * We keep iterator in m->private, since normal case is to
 563          * s_start from where we left off, so we avoid doing
 564          * using get_symbol_offset for every symbol.
 565          */
 566         struct kallsym_iter *iter;
 567         int ret;
 568
 569         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 570         if (!iter)
 571                 return -ENOMEM;
 572         reset_iter(iter, 0);
 573
 574         ret = seq_open(file, &kallsyms_op);
 575         if (ret == 0)
 576                 ((struct seq_file *)file->private_data)->private = iter;
 577         else
 578                 kfree(iter);
 579         return ret;
 580 }
 581
 582 #ifdef  CONFIG_KGDB_KDB
 583 const char *kdb_walk_kallsyms(loff_t *pos)
 584 {
 585         static struct kallsym_iter kdb_walk_kallsyms_iter;
 586         if (*pos == 0) {
 587                 memset(&kdb_walk_kallsyms_iter, 0,
 588                        sizeof(kdb_walk_kallsyms_iter));
 589                 reset_iter(&kdb_walk_kallsyms_iter, 0);
 590         }
 591         while (1) {
 592                 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
 593                         return NULL;
 594                 ++*pos;
 595                 /* Some debugging symbols have no name.  Ignore them. */
 596                 if (kdb_walk_kallsyms_iter.name[0])
 597                         return kdb_walk_kallsyms_iter.name;
 598         }
 599 }
 600 #endif  /* CONFIG_KGDB_KDB */
 601
 602 static const struct file_operations kallsyms_operations = {
 603         .open = kallsyms_open,
 604         .read = seq_read,
 605         .llseek = seq_lseek,
 606         .release = seq_release_private,
 607 };
 608
 609 static int __init kallsyms_init(void)
 610 {
 611         proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
 612         return 0;
 613 }
 614 device_initcall(kallsyms_init);