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
  24 #include <asm/sections.h>
  25
  26 #ifdef CONFIG_KALLSYMS_ALL
  27 #define all_var 1
  28 #else
  29 #define all_var 0
  30 #endif
  31
  32 /* These will be re-linked against their real values during the second link stage */
  33 extern unsigned long kallsyms_addresses[] __attribute__((weak));
  34 extern unsigned long kallsyms_num_syms __attribute__((weak,section("data")));
  35 extern u8 kallsyms_names[] __attribute__((weak));
  36
  37 extern u8 kallsyms_token_table[] __attribute__((weak));
  38 extern u16 kallsyms_token_index[] __attribute__((weak));
  39
  40 extern unsigned long kallsyms_markers[] __attribute__((weak));
  41
  42 static inline int is_kernel_inittext(unsigned long addr)
  43 {
  44         if (addr >= (unsigned long)_sinittext
  45             && addr <= (unsigned long)_einittext)
  46                 return 1;
  47         return 0;
  48 }
  49
  50 static inline int is_kernel_extratext(unsigned long addr)
  51 {
  52         if (addr >= (unsigned long)_sextratext
  53             && addr <= (unsigned long)_eextratext)
  54                 return 1;
  55         return 0;
  56 }
  57
  58 static inline int is_kernel_text(unsigned long addr)
  59 {
  60         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
  61                 return 1;
  62         return in_gate_area_no_task(addr);
  63 }
  64
  65 static inline int is_kernel(unsigned long addr)
  66 {
  67         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
  68                 return 1;
  69         return in_gate_area_no_task(addr);
  70 }
  71
  72 static int is_ksym_addr(unsigned long addr)
  73 {
  74         if (all_var)
  75                 return is_kernel(addr);
  76
  77         return is_kernel_text(addr) || is_kernel_inittext(addr) ||
  78                 is_kernel_extratext(addr);
  79 }
  80
  81 /* expand a compressed symbol data into the resulting uncompressed string,
  82    given the offset to where the symbol is in the compressed stream */
  83 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
  84 {
  85         int len, skipped_first = 0;
  86         u8 *tptr, *data;
  87
  88         /* get the compressed symbol length from the first symbol byte */
  89         data = &kallsyms_names[off];
  90         len = *data;
  91         data++;
  92
  93         /* update the offset to return the offset for the next symbol on
  94          * the compressed stream */
  95         off += len + 1;
  96
  97         /* for every byte on the compressed symbol data, copy the table
  98            entry for that byte */
  99         while(len) {
 100                 tptr = &kallsyms_token_table[ kallsyms_token_index[*data] ];
 101                 data++;
 102                 len--;
 103
 104                 while (*tptr) {
 105                         if(skipped_first) {
 106                                 *result = *tptr;
 107                                 result++;
 108                         } else
 109                                 skipped_first = 1;
 110                         tptr++;
 111                 }
 112         }
 113
 114         *result = '\0';
 115
 116         /* return to offset to the next symbol */
 117         return off;
 118 }
 119
 120 /* get symbol type information. This is encoded as a single char at the
 121  * begining of the symbol name */
 122 static char kallsyms_get_symbol_type(unsigned int off)
 123 {
 124         /* get just the first code, look it up in the token table, and return the
 125          * first char from this token */
 126         return kallsyms_token_table[ kallsyms_token_index[ kallsyms_names[off+1] ] ];
 127 }
 128
 129
 130 /* find the offset on the compressed stream given and index in the
 131  * kallsyms array */
 132 static unsigned int get_symbol_offset(unsigned long pos)
 133 {
 134         u8 *name;
 135         int i;
 136
 137         /* use the closest marker we have. We have markers every 256 positions,
 138          * so that should be close enough */
 139         name = &kallsyms_names[ kallsyms_markers[pos>>8] ];
 140
 141         /* sequentially scan all the symbols up to the point we're searching for.
 142          * Every symbol is stored in a [<len>][<len> bytes of data] format, so we
 143          * just need to add the len to the current pointer for every symbol we
 144          * wish to skip */
 145         for(i = 0; i < (pos&0xFF); i++)
 146                 name = name + (*name) + 1;
 147
 148         return name - kallsyms_names;
 149 }
 150
 151 /* Lookup the address for this symbol. Returns 0 if not found. */
 152 unsigned long kallsyms_lookup_name(const char *name)
 153 {
 154         char namebuf[KSYM_NAME_LEN+1];
 155         unsigned long i;
 156         unsigned int off;
 157
 158         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 159                 off = kallsyms_expand_symbol(off, namebuf);
 160
 161                 if (strcmp(namebuf, name) == 0)
 162                         return kallsyms_addresses[i];
 163         }
 164         return module_kallsyms_lookup_name(name);
 165 }
 166
 167 static unsigned long get_symbol_pos(unsigned long addr,
 168                                     unsigned long *symbolsize,
 169                                     unsigned long *offset)
 170 {
 171         unsigned long symbol_start = 0, symbol_end = 0;
 172         unsigned long i, low, high, mid;
 173
 174         /* This kernel should never had been booted. */
 175         BUG_ON(!kallsyms_addresses);
 176
 177         /* do a binary search on the sorted kallsyms_addresses array */
 178         low = 0;
 179         high = kallsyms_num_syms;
 180
 181         while (high - low > 1) {
 182                 mid = (low + high) / 2;
 183                 if (kallsyms_addresses[mid] <= addr)
 184                         low = mid;
 185                 else
 186                         high = mid;
 187         }
 188
 189         /*
 190          * search for the first aliased symbol. Aliased
 191          * symbols are symbols with the same address
 192          */
 193         while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
 194                 --low;
 195
 196         symbol_start = kallsyms_addresses[low];
 197
 198         /* Search for next non-aliased symbol */
 199         for (i = low + 1; i < kallsyms_num_syms; i++) {
 200                 if (kallsyms_addresses[i] > symbol_start) {
 201                         symbol_end = kallsyms_addresses[i];
 202                         break;
 203                 }
 204         }
 205
 206         /* if we found no next symbol, we use the end of the section */
 207         if (!symbol_end) {
 208                 if (is_kernel_inittext(addr))
 209                         symbol_end = (unsigned long)_einittext;
 210                 else if (all_var)
 211                         symbol_end = (unsigned long)_end;
 212                 else
 213                         symbol_end = (unsigned long)_etext;
 214         }
 215
 216         *symbolsize = symbol_end - symbol_start;
 217         *offset = addr - symbol_start;
 218
 219         return low;
 220 }
 221
 222 /*
 223  * Lookup an address but don't bother to find any names.
 224  */
 225 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
 226                                 unsigned long *offset)
 227 {
 228         if (is_ksym_addr(addr))
 229                 return !!get_symbol_pos(addr, symbolsize, offset);
 230
 231         return !!module_address_lookup(addr, symbolsize, offset, NULL);
 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         const char *msym;
 247
 248         namebuf[KSYM_NAME_LEN] = 0;
 249         namebuf[0] = 0;
 250
 251         if (is_ksym_addr(addr)) {
 252                 unsigned long pos;
 253
 254                 pos = get_symbol_pos(addr, symbolsize, offset);
 255                 /* Grab name */
 256                 kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
 257                 *modname = NULL;
 258                 return namebuf;
 259         }
 260
 261         /* see if it's in a module */
 262         msym = module_address_lookup(addr, symbolsize, offset, modname);
 263         if (msym)
 264                 return strncpy(namebuf, msym, KSYM_NAME_LEN);
 265
 266         return NULL;
 267 }
 268
 269 /* Replace "%s" in format with address, or returns -errno. */
 270 void __print_symbol(const char *fmt, unsigned long address)
 271 {
 272         char *modname;
 273         const char *name;
 274         unsigned long offset, size;
 275         char namebuf[KSYM_NAME_LEN+1];
 276         char buffer[sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +
 277                     2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1];
 278
 279         name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
 280
 281         if (!name)
 282                 sprintf(buffer, "0x%lx", address);
 283         else {
 284                 if (modname)
 285                         sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
 286                                 size, modname);
 287                 else
 288                         sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 289         }
 290         printk(fmt, buffer);
 291 }
 292
 293 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 294 struct kallsym_iter
 295 {
 296         loff_t pos;
 297         struct module *owner;
 298         unsigned long value;
 299         unsigned int nameoff; /* If iterating in core kernel symbols */
 300         char type;
 301         char name[KSYM_NAME_LEN+1];
 302 };
 303
 304 /* Only label it "global" if it is exported. */
 305 static void upcase_if_global(struct kallsym_iter *iter)
 306 {
 307         if (is_exported(iter->name, iter->owner))
 308                 iter->type += 'A' - 'a';
 309 }
 310
 311 static int get_ksymbol_mod(struct kallsym_iter *iter)
 312 {
 313         iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
 314                                          &iter->value, &iter->type,
 315                                          iter->name, sizeof(iter->name));
 316         if (iter->owner == NULL)
 317                 return 0;
 318
 319         upcase_if_global(iter);
 320         return 1;
 321 }
 322
 323 /* Returns space to next name. */
 324 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 325 {
 326         unsigned off = iter->nameoff;
 327
 328         iter->owner = NULL;
 329         iter->value = kallsyms_addresses[iter->pos];
 330
 331         iter->type = kallsyms_get_symbol_type(off);
 332
 333         off = kallsyms_expand_symbol(off, iter->name);
 334
 335         return off - iter->nameoff;
 336 }
 337
 338 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 339 {
 340         iter->name[0] = '\0';
 341         iter->nameoff = get_symbol_offset(new_pos);
 342         iter->pos = new_pos;
 343 }
 344
 345 /* Returns false if pos at or past end of file. */
 346 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 347 {
 348         /* Module symbols can be accessed randomly. */
 349         if (pos >= kallsyms_num_syms) {
 350                 iter->pos = pos;
 351                 return get_ksymbol_mod(iter);
 352         }
 353
 354         /* If we're not on the desired position, reset to new position. */
 355         if (pos != iter->pos)
 356                 reset_iter(iter, pos);
 357
 358         iter->nameoff += get_ksymbol_core(iter);
 359         iter->pos++;
 360
 361         return 1;
 362 }
 363
 364 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 365 {
 366         (*pos)++;
 367
 368         if (!update_iter(m->private, *pos))
 369                 return NULL;
 370         return p;
 371 }
 372
 373 static void *s_start(struct seq_file *m, loff_t *pos)
 374 {
 375         if (!update_iter(m->private, *pos))
 376                 return NULL;
 377         return m->private;
 378 }
 379
 380 static void s_stop(struct seq_file *m, void *p)
 381 {
 382 }
 383
 384 static int s_show(struct seq_file *m, void *p)
 385 {
 386         struct kallsym_iter *iter = m->private;
 387
 388         /* Some debugging symbols have no name.  Ignore them. */
 389         if (!iter->name[0])
 390                 return 0;
 391
 392         if (iter->owner)
 393                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 394                            (int)(2*sizeof(void*)),
 395                            iter->value, iter->type, iter->name,
 396                            module_name(iter->owner));
 397         else
 398                 seq_printf(m, "%0*lx %c %s\n",
 399                            (int)(2*sizeof(void*)),
 400                            iter->value, iter->type, iter->name);
 401         return 0;
 402 }
 403
 404 static struct seq_operations kallsyms_op = {
 405         .start = s_start,
 406         .next = s_next,
 407         .stop = s_stop,
 408         .show = s_show
 409 };
 410
 411 static int kallsyms_open(struct inode *inode, struct file *file)
 412 {
 413         /* We keep iterator in m->private, since normal case is to
 414          * s_start from where we left off, so we avoid doing
 415          * using get_symbol_offset for every symbol */
 416         struct kallsym_iter *iter;
 417         int ret;
 418
 419         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 420         if (!iter)
 421                 return -ENOMEM;
 422         reset_iter(iter, 0);
 423
 424         ret = seq_open(file, &kallsyms_op);
 425         if (ret == 0)
 426                 ((struct seq_file *)file->private_data)->private = iter;
 427         else
 428                 kfree(iter);
 429         return ret;
 430 }
 431
 432 static int kallsyms_release(struct inode *inode, struct file *file)
 433 {
 434         struct seq_file *m = (struct seq_file *)file->private_data;
 435         kfree(m->private);
 436         return seq_release(inode, file);
 437 }
 438
 439 static struct file_operations kallsyms_operations = {
 440         .open = kallsyms_open,
 441         .read = seq_read,
 442         .llseek = seq_lseek,
 443         .release = kallsyms_release,
 444 };
 445
 446 static int __init kallsyms_init(void)
 447 {
 448         struct proc_dir_entry *entry;
 449
 450         entry = create_proc_entry("kallsyms", 0444, NULL);
 451         if (entry)
 452                 entry->proc_fops = &kallsyms_operations;
 453         return 0;
 454 }
 455 __initcall(kallsyms_init);
 456
 457 EXPORT_SYMBOL(__print_symbol);