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 }
 264
 265 int lookup_symbol_name(unsigned long addr, char *symname)
 266 {
 267         symname[0] = '\0';
 268         symname[KSYM_NAME_LEN - 1] = '\0';
 269
 270         if (is_ksym_addr(addr)) {
 271                 unsigned long pos;
 272
 273                 pos = get_symbol_pos(addr, NULL, NULL);
 274                 /* Grab name */
 275                 kallsyms_expand_symbol(get_symbol_offset(pos), symname);
 276                 return 0;
 277         }
 278         /* see if it's in a module */
 279         return lookup_module_symbol_name(addr, symname);
 280 }
 281
 282 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 283                         unsigned long *offset, char *modname, char *name)
 284 {
 285         name[0] = '\0';
 286         name[KSYM_NAME_LEN - 1] = '\0';
 287
 288         if (is_ksym_addr(addr)) {
 289                 unsigned long pos;
 290
 291                 pos = get_symbol_pos(addr, size, offset);
 292                 /* Grab name */
 293                 kallsyms_expand_symbol(get_symbol_offset(pos), name);
 294                 modname[0] = '\0';
 295                 return 0;
 296         }
 297         /* see if it's in a module */
 298         return lookup_module_symbol_attrs(addr, size, offset, modname, name);
 299 }
 300
 301 /* Look up a kernel symbol and return it in a text buffer. */
 302 int sprint_symbol(char *buffer, unsigned long address)
 303 {
 304         char *modname;
 305         const char *name;
 306         unsigned long offset, size;
 307         int len;
 308
 309         name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
 310         if (!name)
 311                 return sprintf(buffer, "0x%lx", address);
 312
 313         if (name != buffer)
 314                 strcpy(buffer, name);
 315         len = strlen(buffer);
 316         buffer += len;
 317
 318         if (modname)
 319                 len += sprintf(buffer, "+%#lx/%#lx [%s]",
 320                                                 offset, size, modname);
 321         else
 322                 len += sprintf(buffer, "+%#lx/%#lx", offset, size);
 323
 324         return len;
 325 }
 326
 327 /* Look up a kernel symbol and print it to the kernel messages. */
 328 void __print_symbol(const char *fmt, unsigned long address)
 329 {
 330         char buffer[KSYM_SYMBOL_LEN];
 331
 332         sprint_symbol(buffer, address);
 333
 334         printk(fmt, buffer);
 335 }
 336
 337 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 338 struct kallsym_iter
 339 {
 340         loff_t pos;
 341         unsigned long value;
 342         unsigned int nameoff; /* If iterating in core kernel symbols */
 343         char type;
 344         char name[KSYM_NAME_LEN];
 345         char module_name[MODULE_NAME_LEN];
 346         int exported;
 347 };
 348
 349 static int get_ksymbol_mod(struct kallsym_iter *iter)
 350 {
 351         if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
 352                                 &iter->type, iter->name, iter->module_name,
 353                                 &iter->exported) < 0)
 354                 return 0;
 355         return 1;
 356 }
 357
 358 /* Returns space to next name. */
 359 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 360 {
 361         unsigned off = iter->nameoff;
 362
 363         iter->module_name[0] = '\0';
 364         iter->value = kallsyms_addresses[iter->pos];
 365
 366         iter->type = kallsyms_get_symbol_type(off);
 367
 368         off = kallsyms_expand_symbol(off, iter->name);
 369
 370         return off - iter->nameoff;
 371 }
 372
 373 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 374 {
 375         iter->name[0] = '\0';
 376         iter->nameoff = get_symbol_offset(new_pos);
 377         iter->pos = new_pos;
 378 }
 379
 380 /* Returns false if pos at or past end of file. */
 381 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 382 {
 383         /* Module symbols can be accessed randomly. */
 384         if (pos >= kallsyms_num_syms) {
 385                 iter->pos = pos;
 386                 return get_ksymbol_mod(iter);
 387         }
 388
 389         /* If we're not on the desired position, reset to new position. */
 390         if (pos != iter->pos)
 391                 reset_iter(iter, pos);
 392
 393         iter->nameoff += get_ksymbol_core(iter);
 394         iter->pos++;
 395
 396         return 1;
 397 }
 398
 399 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 400 {
 401         (*pos)++;
 402
 403         if (!update_iter(m->private, *pos))
 404                 return NULL;
 405         return p;
 406 }
 407
 408 static void *s_start(struct seq_file *m, loff_t *pos)
 409 {
 410         if (!update_iter(m->private, *pos))
 411                 return NULL;
 412         return m->private;
 413 }
 414
 415 static void s_stop(struct seq_file *m, void *p)
 416 {
 417 }
 418
 419 static int s_show(struct seq_file *m, void *p)
 420 {
 421         struct kallsym_iter *iter = m->private;
 422
 423         /* Some debugging symbols have no name.  Ignore them. */
 424         if (!iter->name[0])
 425                 return 0;
 426
 427         if (iter->module_name[0]) {
 428                 char type;
 429
 430                 /* Label it "global" if it is exported,
 431                  * "local" if not exported. */
 432                 type = iter->exported ? toupper(iter->type) :
 433                                         tolower(iter->type);
 434                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 435                            (int)(2*sizeof(void*)),
 436                            iter->value, type, iter->name, iter->module_name);
 437         } else
 438                 seq_printf(m, "%0*lx %c %s\n",
 439                            (int)(2*sizeof(void*)),
 440                            iter->value, iter->type, iter->name);
 441         return 0;
 442 }
 443
 444 static const struct seq_operations kallsyms_op = {
 445         .start = s_start,
 446         .next = s_next,
 447         .stop = s_stop,
 448         .show = s_show
 449 };
 450
 451 static int kallsyms_open(struct inode *inode, struct file *file)
 452 {
 453         /* We keep iterator in m->private, since normal case is to
 454          * s_start from where we left off, so we avoid doing
 455          * using get_symbol_offset for every symbol */
 456         struct kallsym_iter *iter;
 457         int ret;
 458
 459         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 460         if (!iter)
 461                 return -ENOMEM;
 462         reset_iter(iter, 0);
 463
 464         ret = seq_open(file, &kallsyms_op);
 465         if (ret == 0)
 466                 ((struct seq_file *)file->private_data)->private = iter;
 467         else
 468                 kfree(iter);
 469         return ret;
 470 }
 471
 472 static const struct file_operations kallsyms_operations = {
 473         .open = kallsyms_open,
 474         .read = seq_read,
 475         .llseek = seq_lseek,
 476         .release = seq_release_private,
 477 };
 478
 479 static int __init kallsyms_init(void)
 480 {
 481         proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
 482         return 0;
 483 }
 484 __initcall(kallsyms_init);
 485
 486 EXPORT_SYMBOL(__print_symbol);
 487 EXPORT_SYMBOL_GPL(sprint_symbol);