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+1];
 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         *symbolsize = symbol_end - symbol_start;
 218         *offset = addr - symbol_start;
 219
 220         return low;
 221 }
 222
 223 /*
 224  * Lookup an address but don't bother to find any names.
 225  */
 226 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
 227                                 unsigned long *offset)
 228 {
 229         if (is_ksym_addr(addr))
 230                 return !!get_symbol_pos(addr, symbolsize, offset);
 231
 232         return !!module_address_lookup(addr, symbolsize, offset, NULL);
 233 }
 234
 235 /*
 236  * Lookup an address
 237  * - modname is set to NULL if it's in the kernel
 238  * - we guarantee that the returned name is valid until we reschedule even if
 239  *   it resides in a module
 240  * - we also guarantee that modname will be valid until rescheduled
 241  */
 242 const char *kallsyms_lookup(unsigned long addr,
 243                             unsigned long *symbolsize,
 244                             unsigned long *offset,
 245                             char **modname, char *namebuf)
 246 {
 247         const char *msym;
 248
 249         namebuf[KSYM_NAME_LEN] = 0;
 250         namebuf[0] = 0;
 251
 252         if (is_ksym_addr(addr)) {
 253                 unsigned long pos;
 254
 255                 pos = get_symbol_pos(addr, symbolsize, offset);
 256                 /* Grab name */
 257                 kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
 258                 *modname = NULL;
 259                 return namebuf;
 260         }
 261
 262         /* see if it's in a module */
 263         msym = module_address_lookup(addr, symbolsize, offset, modname);
 264         if (msym)
 265                 return strncpy(namebuf, msym, KSYM_NAME_LEN);
 266
 267         return NULL;
 268 }
 269
 270 /* Look up a kernel symbol and return it in a text buffer. */
 271 int sprint_symbol(char *buffer, unsigned long address)
 272 {
 273         char *modname;
 274         const char *name;
 275         unsigned long offset, size;
 276         char namebuf[KSYM_NAME_LEN+1];
 277
 278         name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
 279         if (!name)
 280                 return sprintf(buffer, "0x%lx", address);
 281         else {
 282                 if (modname)
 283                         return sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
 284                                 size, modname);
 285                 else
 286                         return sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 287         }
 288 }
 289
 290 /* Look up a kernel symbol and print it to the kernel messages. */
 291 void __print_symbol(const char *fmt, unsigned long address)
 292 {
 293         char buffer[KSYM_SYMBOL_LEN];
 294
 295         sprint_symbol(buffer, address);
 296
 297         printk(fmt, buffer);
 298 }
 299
 300 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 301 struct kallsym_iter
 302 {
 303         loff_t pos;
 304         struct module *owner;
 305         unsigned long value;
 306         unsigned int nameoff; /* If iterating in core kernel symbols */
 307         char type;
 308         char name[KSYM_NAME_LEN+1];
 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         /* Label it "global" if it is exported, "local" if not exported. */
 320         iter->type = is_exported(iter->name, iter->owner)
 321                 ? toupper(iter->type) : tolower(iter->type);
 322
 323         return 1;
 324 }
 325
 326 /* Returns space to next name. */
 327 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 328 {
 329         unsigned off = iter->nameoff;
 330
 331         iter->owner = NULL;
 332         iter->value = kallsyms_addresses[iter->pos];
 333
 334         iter->type = kallsyms_get_symbol_type(off);
 335
 336         off = kallsyms_expand_symbol(off, iter->name);
 337
 338         return off - iter->nameoff;
 339 }
 340
 341 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 342 {
 343         iter->name[0] = '\0';
 344         iter->nameoff = get_symbol_offset(new_pos);
 345         iter->pos = new_pos;
 346 }
 347
 348 /* Returns false if pos at or past end of file. */
 349 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 350 {
 351         /* Module symbols can be accessed randomly. */
 352         if (pos >= kallsyms_num_syms) {
 353                 iter->pos = pos;
 354                 return get_ksymbol_mod(iter);
 355         }
 356
 357         /* If we're not on the desired position, reset to new position. */
 358         if (pos != iter->pos)
 359                 reset_iter(iter, pos);
 360
 361         iter->nameoff += get_ksymbol_core(iter);
 362         iter->pos++;
 363
 364         return 1;
 365 }
 366
 367 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 368 {
 369         (*pos)++;
 370
 371         if (!update_iter(m->private, *pos))
 372                 return NULL;
 373         return p;
 374 }
 375
 376 static void *s_start(struct seq_file *m, loff_t *pos)
 377 {
 378         if (!update_iter(m->private, *pos))
 379                 return NULL;
 380         return m->private;
 381 }
 382
 383 static void s_stop(struct seq_file *m, void *p)
 384 {
 385 }
 386
 387 static int s_show(struct seq_file *m, void *p)
 388 {
 389         struct kallsym_iter *iter = m->private;
 390
 391         /* Some debugging symbols have no name.  Ignore them. */
 392         if (!iter->name[0])
 393                 return 0;
 394
 395         if (iter->owner)
 396                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 397                            (int)(2*sizeof(void*)),
 398                            iter->value, iter->type, iter->name,
 399                            module_name(iter->owner));
 400         else
 401                 seq_printf(m, "%0*lx %c %s\n",
 402                            (int)(2*sizeof(void*)),
 403                            iter->value, iter->type, iter->name);
 404         return 0;
 405 }
 406
 407 static const struct seq_operations kallsyms_op = {
 408         .start = s_start,
 409         .next = s_next,
 410         .stop = s_stop,
 411         .show = s_show
 412 };
 413
 414 static int kallsyms_open(struct inode *inode, struct file *file)
 415 {
 416         /* We keep iterator in m->private, since normal case is to
 417          * s_start from where we left off, so we avoid doing
 418          * using get_symbol_offset for every symbol */
 419         struct kallsym_iter *iter;
 420         int ret;
 421
 422         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 423         if (!iter)
 424                 return -ENOMEM;
 425         reset_iter(iter, 0);
 426
 427         ret = seq_open(file, &kallsyms_op);
 428         if (ret == 0)
 429                 ((struct seq_file *)file->private_data)->private = iter;
 430         else
 431                 kfree(iter);
 432         return ret;
 433 }
 434
 435 static int kallsyms_release(struct inode *inode, struct file *file)
 436 {
 437         struct seq_file *m = (struct seq_file *)file->private_data;
 438         kfree(m->private);
 439         return seq_release(inode, file);
 440 }
 441
 442 static const struct file_operations kallsyms_operations = {
 443         .open = kallsyms_open,
 444         .read = seq_read,
 445         .llseek = seq_lseek,
 446         .release = kallsyms_release,
 447 };
 448
 449 static int __init kallsyms_init(void)
 450 {
 451         struct proc_dir_entry *entry;
 452
 453         entry = create_proc_entry("kallsyms", 0444, NULL);
 454         if (entry)
 455                 entry->proc_fops = &kallsyms_operations;
 456         return 0;
 457 }
 458 __initcall(kallsyms_init);
 459
 460 EXPORT_SYMBOL(__print_symbol);
 461 EXPORT_SYMBOL_GPL(sprint_symbol);