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