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