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