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 /* expand a compressed symbol data into the resulting uncompressed string,
  73    given the offset to where the symbol is in the compressed stream */
  74 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
  75 {
  76         int len, skipped_first = 0;
  77         u8 *tptr, *data;
  78
  79         /* get the compressed symbol length from the first symbol byte */
  80         data = &kallsyms_names[off];
  81         len = *data;
  82         data++;
  83
  84         /* update the offset to return the offset for the next symbol on
  85          * the compressed stream */
  86         off += len + 1;
  87
  88         /* for every byte on the compressed symbol data, copy the table
  89            entry for that byte */
  90         while(len) {
  91                 tptr = &kallsyms_token_table[ kallsyms_token_index[*data] ];
  92                 data++;
  93                 len--;
  94
  95                 while (*tptr) {
  96                         if(skipped_first) {
  97                                 *result = *tptr;
  98                                 result++;
  99                         } else
 100                                 skipped_first = 1;
 101                         tptr++;
 102                 }
 103         }
 104
 105         *result = '\0';
 106
 107         /* return to offset to the next symbol */
 108         return off;
 109 }
 110
 111 /* get symbol type information. This is encoded as a single char at the
 112  * begining of the symbol name */
 113 static char kallsyms_get_symbol_type(unsigned int off)
 114 {
 115         /* get just the first code, look it up in the token table, and return the
 116          * first char from this token */
 117         return kallsyms_token_table[ kallsyms_token_index[ kallsyms_names[off+1] ] ];
 118 }
 119
 120
 121 /* find the offset on the compressed stream given and index in the
 122  * kallsyms array */
 123 static unsigned int get_symbol_offset(unsigned long pos)
 124 {
 125         u8 *name;
 126         int i;
 127
 128         /* use the closest marker we have. We have markers every 256 positions,
 129          * so that should be close enough */
 130         name = &kallsyms_names[ kallsyms_markers[pos>>8] ];
 131
 132         /* sequentially scan all the symbols up to the point we're searching for.
 133          * Every symbol is stored in a [<len>][<len> bytes of data] format, so we
 134          * just need to add the len to the current pointer for every symbol we
 135          * wish to skip */
 136         for(i = 0; i < (pos&0xFF); i++)
 137                 name = name + (*name) + 1;
 138
 139         return name - kallsyms_names;
 140 }
 141
 142 /* Lookup the address for this symbol. Returns 0 if not found. */
 143 unsigned long kallsyms_lookup_name(const char *name)
 144 {
 145         char namebuf[KSYM_NAME_LEN+1];
 146         unsigned long i;
 147         unsigned int off;
 148
 149         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 150                 off = kallsyms_expand_symbol(off, namebuf);
 151
 152                 if (strcmp(namebuf, name) == 0)
 153                         return kallsyms_addresses[i];
 154         }
 155         return module_kallsyms_lookup_name(name);
 156 }
 157 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
 158
 159 /*
 160  * Lookup an address
 161  * - modname is set to NULL if it's in the kernel
 162  * - we guarantee that the returned name is valid until we reschedule even if
 163  *   it resides in a module
 164  * - we also guarantee that modname will be valid until rescheduled
 165  */
 166 const char *kallsyms_lookup(unsigned long addr,
 167                             unsigned long *symbolsize,
 168                             unsigned long *offset,
 169                             char **modname, char *namebuf)
 170 {
 171         unsigned long i, low, high, mid;
 172         const char *msym;
 173
 174         /* This kernel should never had been booted. */
 175         BUG_ON(!kallsyms_addresses);
 176
 177         namebuf[KSYM_NAME_LEN] = 0;
 178         namebuf[0] = 0;
 179
 180         if ((all_var && is_kernel(addr)) ||
 181             (!all_var && (is_kernel_text(addr) || is_kernel_inittext(addr) ||
 182                                 is_kernel_extratext(addr)))) {
 183                 unsigned long symbol_end = 0;
 184
 185                 /* do a binary search on the sorted kallsyms_addresses array */
 186                 low = 0;
 187                 high = kallsyms_num_syms;
 188
 189                 while (high-low > 1) {
 190                         mid = (low + high) / 2;
 191                         if (kallsyms_addresses[mid] <= addr) low = mid;
 192                         else high = mid;
 193                 }
 194
 195                 /* search for the first aliased symbol. Aliased symbols are
 196                    symbols with the same address */
 197                 while (low && kallsyms_addresses[low - 1] == kallsyms_addresses[low])
 198                         --low;
 199
 200                 /* Grab name */
 201                 kallsyms_expand_symbol(get_symbol_offset(low), namebuf);
 202
 203                 /* Search for next non-aliased symbol */
 204                 for (i = low + 1; i < kallsyms_num_syms; i++) {
 205                         if (kallsyms_addresses[i] > kallsyms_addresses[low]) {
 206                                 symbol_end = kallsyms_addresses[i];
 207                                 break;
 208                         }
 209                 }
 210
 211                 /* if we found no next symbol, we use the end of the section */
 212                 if (!symbol_end) {
 213                         if (is_kernel_inittext(addr))
 214                                 symbol_end = (unsigned long)_einittext;
 215                         else
 216                                 symbol_end = all_var ? (unsigned long)_end : (unsigned long)_etext;
 217                 }
 218
 219                 *symbolsize = symbol_end - kallsyms_addresses[low];
 220                 *modname = NULL;
 221                 *offset = addr - kallsyms_addresses[low];
 222                 return namebuf;
 223         }
 224
 225         /* see if it's in a module */
 226         msym = module_address_lookup(addr, symbolsize, offset, modname);
 227         if (msym)
 228                 return strncpy(namebuf, msym, KSYM_NAME_LEN);
 229
 230         return NULL;
 231 }
 232
 233 /* Replace "%s" in format with address, or returns -errno. */
 234 void __print_symbol(const char *fmt, unsigned long address)
 235 {
 236         char *modname;
 237         const char *name;
 238         unsigned long offset, size;
 239         char namebuf[KSYM_NAME_LEN+1];
 240         char buffer[sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +
 241                     2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1];
 242
 243         name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
 244
 245         if (!name)
 246                 sprintf(buffer, "0x%lx", address);
 247         else {
 248                 if (modname)
 249                         sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
 250                                 size, modname);
 251                 else
 252                         sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 253         }
 254         printk(fmt, buffer);
 255 }
 256
 257 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 258 struct kallsym_iter
 259 {
 260         loff_t pos;
 261         struct module *owner;
 262         unsigned long value;
 263         unsigned int nameoff; /* If iterating in core kernel symbols */
 264         char type;
 265         char name[KSYM_NAME_LEN+1];
 266 };
 267
 268 /* Only label it "global" if it is exported. */
 269 static void upcase_if_global(struct kallsym_iter *iter)
 270 {
 271         if (is_exported(iter->name, iter->owner))
 272                 iter->type += 'A' - 'a';
 273 }
 274
 275 static int get_ksymbol_mod(struct kallsym_iter *iter)
 276 {
 277         iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
 278                                          &iter->value,
 279                                          &iter->type, iter->name);
 280         if (iter->owner == NULL)
 281                 return 0;
 282
 283         upcase_if_global(iter);
 284         return 1;
 285 }
 286
 287 /* Returns space to next name. */
 288 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 289 {
 290         unsigned off = iter->nameoff;
 291
 292         iter->owner = NULL;
 293         iter->value = kallsyms_addresses[iter->pos];
 294
 295         iter->type = kallsyms_get_symbol_type(off);
 296
 297         off = kallsyms_expand_symbol(off, iter->name);
 298
 299         return off - iter->nameoff;
 300 }
 301
 302 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 303 {
 304         iter->name[0] = '\0';
 305         iter->nameoff = get_symbol_offset(new_pos);
 306         iter->pos = new_pos;
 307 }
 308
 309 /* Returns false if pos at or past end of file. */
 310 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 311 {
 312         /* Module symbols can be accessed randomly. */
 313         if (pos >= kallsyms_num_syms) {
 314                 iter->pos = pos;
 315                 return get_ksymbol_mod(iter);
 316         }
 317
 318         /* If we're not on the desired position, reset to new position. */
 319         if (pos != iter->pos)
 320                 reset_iter(iter, pos);
 321
 322         iter->nameoff += get_ksymbol_core(iter);
 323         iter->pos++;
 324
 325         return 1;
 326 }
 327
 328 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 329 {
 330         (*pos)++;
 331
 332         if (!update_iter(m->private, *pos))
 333                 return NULL;
 334         return p;
 335 }
 336
 337 static void *s_start(struct seq_file *m, loff_t *pos)
 338 {
 339         if (!update_iter(m->private, *pos))
 340                 return NULL;
 341         return m->private;
 342 }
 343
 344 static void s_stop(struct seq_file *m, void *p)
 345 {
 346 }
 347
 348 static int s_show(struct seq_file *m, void *p)
 349 {
 350         struct kallsym_iter *iter = m->private;
 351
 352         /* Some debugging symbols have no name.  Ignore them. */
 353         if (!iter->name[0])
 354                 return 0;
 355
 356         if (iter->owner)
 357                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 358                            (int)(2*sizeof(void*)),
 359                            iter->value, iter->type, iter->name,
 360                            module_name(iter->owner));
 361         else
 362                 seq_printf(m, "%0*lx %c %s\n",
 363                            (int)(2*sizeof(void*)),
 364                            iter->value, iter->type, iter->name);
 365         return 0;
 366 }
 367
 368 static struct seq_operations kallsyms_op = {
 369         .start = s_start,
 370         .next = s_next,
 371         .stop = s_stop,
 372         .show = s_show
 373 };
 374
 375 static int kallsyms_open(struct inode *inode, struct file *file)
 376 {
 377         /* We keep iterator in m->private, since normal case is to
 378          * s_start from where we left off, so we avoid doing
 379          * using get_symbol_offset for every symbol */
 380         struct kallsym_iter *iter;
 381         int ret;
 382
 383         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 384         if (!iter)
 385                 return -ENOMEM;
 386         reset_iter(iter, 0);
 387
 388         ret = seq_open(file, &kallsyms_op);
 389         if (ret == 0)
 390                 ((struct seq_file *)file->private_data)->private = iter;
 391         else
 392                 kfree(iter);
 393         return ret;
 394 }
 395
 396 static int kallsyms_release(struct inode *inode, struct file *file)
 397 {
 398         struct seq_file *m = (struct seq_file *)file->private_data;
 399         kfree(m->private);
 400         return seq_release(inode, file);
 401 }
 402
 403 static struct file_operations kallsyms_operations = {
 404         .open = kallsyms_open,
 405         .read = seq_read,
 406         .llseek = seq_lseek,
 407         .release = kallsyms_release,
 408 };
 409
 410 static int __init kallsyms_init(void)
 411 {
 412         struct proc_dir_entry *entry;
 413
 414         entry = create_proc_entry("kallsyms", 0444, NULL);
 415         if (entry)
 416                 entry->proc_fops = &kallsyms_operations;
 417         return 0;
 418 }
 419 __initcall(kallsyms_init);
 420
 421 EXPORT_SYMBOL(__print_symbol);