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
 158 /*
 159  * Lookup an address
 160  * - modname is set to NULL if it's in the kernel
 161  * - we guarantee that the returned name is valid until we reschedule even if
 162  *   it resides in a module
 163  * - we also guarantee that modname will be valid until rescheduled
 164  */
 165 const char *kallsyms_lookup(unsigned long addr,
 166                             unsigned long *symbolsize,
 167                             unsigned long *offset,
 168                             char **modname, char *namebuf)
 169 {
 170         unsigned long i, low, high, mid;
 171         const char *msym;
 172
 173         /* This kernel should never had been booted. */
 174         BUG_ON(!kallsyms_addresses);
 175
 176         namebuf[KSYM_NAME_LEN] = 0;
 177         namebuf[0] = 0;
 178
 179         if ((all_var && is_kernel(addr)) ||
 180             (!all_var && (is_kernel_text(addr) || is_kernel_inittext(addr) ||
 181                                 is_kernel_extratext(addr)))) {
 182                 unsigned long symbol_end = 0;
 183
 184                 /* do a binary search on the sorted kallsyms_addresses array */
 185                 low = 0;
 186                 high = kallsyms_num_syms;
 187
 188                 while (high-low > 1) {
 189                         mid = (low + high) / 2;
 190                         if (kallsyms_addresses[mid] <= addr) low = mid;
 191                         else high = mid;
 192                 }
 193
 194                 /* search for the first aliased symbol. Aliased symbols are
 195                    symbols with the same address */
 196                 while (low && kallsyms_addresses[low - 1] == kallsyms_addresses[low])
 197                         --low;
 198
 199                 /* Grab name */
 200                 kallsyms_expand_symbol(get_symbol_offset(low), namebuf);
 201
 202                 /* Search for next non-aliased symbol */
 203                 for (i = low + 1; i < kallsyms_num_syms; i++) {
 204                         if (kallsyms_addresses[i] > kallsyms_addresses[low]) {
 205                                 symbol_end = kallsyms_addresses[i];
 206                                 break;
 207                         }
 208                 }
 209
 210                 /* if we found no next symbol, we use the end of the section */
 211                 if (!symbol_end) {
 212                         if (is_kernel_inittext(addr))
 213                                 symbol_end = (unsigned long)_einittext;
 214                         else
 215                                 symbol_end = all_var ? (unsigned long)_end : (unsigned long)_etext;
 216                 }
 217
 218                 *symbolsize = symbol_end - kallsyms_addresses[low];
 219                 *modname = NULL;
 220                 *offset = addr - kallsyms_addresses[low];
 221                 return namebuf;
 222         }
 223
 224         /* see if it's in a module */
 225         msym = module_address_lookup(addr, symbolsize, offset, modname);
 226         if (msym)
 227                 return strncpy(namebuf, msym, KSYM_NAME_LEN);
 228
 229         return NULL;
 230 }
 231
 232 /* Replace "%s" in format with address, or returns -errno. */
 233 void __print_symbol(const char *fmt, unsigned long address)
 234 {
 235         char *modname;
 236         const char *name;
 237         unsigned long offset, size;
 238         char namebuf[KSYM_NAME_LEN+1];
 239         char buffer[sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +
 240                     2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1];
 241
 242         name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
 243
 244         if (!name)
 245                 sprintf(buffer, "0x%lx", address);
 246         else {
 247                 if (modname)
 248                         sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
 249                                 size, modname);
 250                 else
 251                         sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 252         }
 253         printk(fmt, buffer);
 254 }
 255
 256 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 257 struct kallsym_iter
 258 {
 259         loff_t pos;
 260         struct module *owner;
 261         unsigned long value;
 262         unsigned int nameoff; /* If iterating in core kernel symbols */
 263         char type;
 264         char name[KSYM_NAME_LEN+1];
 265 };
 266
 267 /* Only label it "global" if it is exported. */
 268 static void upcase_if_global(struct kallsym_iter *iter)
 269 {
 270         if (is_exported(iter->name, iter->owner))
 271                 iter->type += 'A' - 'a';
 272 }
 273
 274 static int get_ksymbol_mod(struct kallsym_iter *iter)
 275 {
 276         iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
 277                                          &iter->value, &iter->type,
 278                                          iter->name, sizeof(iter->name));
 279         if (iter->owner == NULL)
 280                 return 0;
 281
 282         upcase_if_global(iter);
 283         return 1;
 284 }
 285
 286 /* Returns space to next name. */
 287 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 288 {
 289         unsigned off = iter->nameoff;
 290
 291         iter->owner = NULL;
 292         iter->value = kallsyms_addresses[iter->pos];
 293
 294         iter->type = kallsyms_get_symbol_type(off);
 295
 296         off = kallsyms_expand_symbol(off, iter->name);
 297
 298         return off - iter->nameoff;
 299 }
 300
 301 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 302 {
 303         iter->name[0] = '\0';
 304         iter->nameoff = get_symbol_offset(new_pos);
 305         iter->pos = new_pos;
 306 }
 307
 308 /* Returns false if pos at or past end of file. */
 309 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 310 {
 311         /* Module symbols can be accessed randomly. */
 312         if (pos >= kallsyms_num_syms) {
 313                 iter->pos = pos;
 314                 return get_ksymbol_mod(iter);
 315         }
 316
 317         /* If we're not on the desired position, reset to new position. */
 318         if (pos != iter->pos)
 319                 reset_iter(iter, pos);
 320
 321         iter->nameoff += get_ksymbol_core(iter);
 322         iter->pos++;
 323
 324         return 1;
 325 }
 326
 327 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 328 {
 329         (*pos)++;
 330
 331         if (!update_iter(m->private, *pos))
 332                 return NULL;
 333         return p;
 334 }
 335
 336 static void *s_start(struct seq_file *m, loff_t *pos)
 337 {
 338         if (!update_iter(m->private, *pos))
 339                 return NULL;
 340         return m->private;
 341 }
 342
 343 static void s_stop(struct seq_file *m, void *p)
 344 {
 345 }
 346
 347 static int s_show(struct seq_file *m, void *p)
 348 {
 349         struct kallsym_iter *iter = m->private;
 350
 351         /* Some debugging symbols have no name.  Ignore them. */
 352         if (!iter->name[0])
 353                 return 0;
 354
 355         if (iter->owner)
 356                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 357                            (int)(2*sizeof(void*)),
 358                            iter->value, iter->type, iter->name,
 359                            module_name(iter->owner));
 360         else
 361                 seq_printf(m, "%0*lx %c %s\n",
 362                            (int)(2*sizeof(void*)),
 363                            iter->value, iter->type, iter->name);
 364         return 0;
 365 }
 366
 367 static struct seq_operations kallsyms_op = {
 368         .start = s_start,
 369         .next = s_next,
 370         .stop = s_stop,
 371         .show = s_show
 372 };
 373
 374 static int kallsyms_open(struct inode *inode, struct file *file)
 375 {
 376         /* We keep iterator in m->private, since normal case is to
 377          * s_start from where we left off, so we avoid doing
 378          * using get_symbol_offset for every symbol */
 379         struct kallsym_iter *iter;
 380         int ret;
 381
 382         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 383         if (!iter)
 384                 return -ENOMEM;
 385         reset_iter(iter, 0);
 386
 387         ret = seq_open(file, &kallsyms_op);
 388         if (ret == 0)
 389                 ((struct seq_file *)file->private_data)->private = iter;
 390         else
 391                 kfree(iter);
 392         return ret;
 393 }
 394
 395 static int kallsyms_release(struct inode *inode, struct file *file)
 396 {
 397         struct seq_file *m = (struct seq_file *)file->private_data;
 398         kfree(m->private);
 399         return seq_release(inode, file);
 400 }
 401
 402 static struct file_operations kallsyms_operations = {
 403         .open = kallsyms_open,
 404         .read = seq_read,
 405         .llseek = seq_lseek,
 406         .release = kallsyms_release,
 407 };
 408
 409 static int __init kallsyms_init(void)
 410 {
 411         struct proc_dir_entry *entry;
 412
 413         entry = create_proc_entry("kallsyms", 0444, NULL);
 414         if (entry)
 415                 entry->proc_fops = &kallsyms_operations;
 416         return 0;
 417 }
 418 __initcall(kallsyms_init);
 419
 420 EXPORT_SYMBOL(__print_symbol);