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