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