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
  22 /* These will be re-linked against their real values during the second link stage */
  23 extern unsigned long kallsyms_addresses[] __attribute__((weak));
  24 extern unsigned long kallsyms_num_syms __attribute__((weak));
  25 extern u8 kallsyms_names[] __attribute__((weak));
  26
  27 extern u8 kallsyms_token_table[] __attribute__((weak));
  28 extern u16 kallsyms_token_index[] __attribute__((weak));
  29
  30 extern unsigned long kallsyms_markers[] __attribute__((weak));
  31
  32 /* Defined by the linker script. */
  33 extern char _stext[], _etext[], _sinittext[], _einittext[];
  34
  35 static inline int is_kernel_inittext(unsigned long addr)
  36 {
  37         if (addr >= (unsigned long)_sinittext
  38             && addr <= (unsigned long)_einittext)
  39                 return 1;
  40         return 0;
  41 }
  42
  43 static inline int is_kernel_text(unsigned long addr)
  44 {
  45         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
  46                 return 1;
  47         return 0;
  48 }
  49
  50 /* expand a compressed symbol data into the resulting uncompressed string,
  51    given the offset to where the symbol is in the compressed stream */
  52 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
  53 {
  54         int len, skipped_first = 0;
  55         u8 *tptr, *data;
  56
  57         /* get the compressed symbol length from the first symbol byte */
  58         data = &kallsyms_names[off];
  59         len = *data;
  60         data++;
  61
  62         /* update the offset to return the offset for the next symbol on
  63          * the compressed stream */
  64         off += len + 1;
  65
  66         /* for every byte on the compressed symbol data, copy the table
  67            entry for that byte */
  68         while(len) {
  69                 tptr = &kallsyms_token_table[ kallsyms_token_index[*data] ];
  70                 data++;
  71                 len--;
  72
  73                 while (*tptr) {
  74                         if(skipped_first) {
  75                                 *result = *tptr;
  76                                 result++;
  77                         } else
  78                                 skipped_first = 1;
  79                         tptr++;
  80                 }
  81         }
  82
  83         *result = '\0';
  84
  85         /* return to offset to the next symbol */
  86         return off;
  87 }
  88
  89 /* get symbol type information. This is encoded as a single char at the
  90  * begining of the symbol name */
  91 static char kallsyms_get_symbol_type(unsigned int off)
  92 {
  93         /* get just the first code, look it up in the token table, and return the
  94          * first char from this token */
  95         return kallsyms_token_table[ kallsyms_token_index[ kallsyms_names[off+1] ] ];
  96 }
  97
  98
  99 /* find the offset on the compressed stream given and index in the
 100  * kallsyms array */
 101 static unsigned int get_symbol_offset(unsigned long pos)
 102 {
 103         u8 *name;
 104         int i;
 105
 106         /* use the closest marker we have. We have markers every 256 positions,
 107          * so that should be close enough */
 108         name = &kallsyms_names[ kallsyms_markers[pos>>8] ];
 109
 110         /* sequentially scan all the symbols up to the point we're searching for.
 111          * Every symbol is stored in a [<len>][<len> bytes of data] format, so we
 112          * just need to add the len to the current pointer for every symbol we
 113          * wish to skip */
 114         for(i = 0; i < (pos&0xFF); i++)
 115                 name = name + (*name) + 1;
 116
 117         return name - kallsyms_names;
 118 }
 119
 120 /* Lookup the address for this symbol. Returns 0 if not found. */
 121 unsigned long kallsyms_lookup_name(const char *name)
 122 {
 123         char namebuf[KSYM_NAME_LEN+1];
 124         unsigned long i;
 125         unsigned int off;
 126
 127         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 128                 off = kallsyms_expand_symbol(off, namebuf);
 129
 130                 if (strcmp(namebuf, name) == 0)
 131                         return kallsyms_addresses[i];
 132         }
 133         return module_kallsyms_lookup_name(name);
 134 }
 135
 136 /* Lookup an address.  modname is set to NULL if it's in the kernel. */
 137 const char *kallsyms_lookup(unsigned long addr,
 138                             unsigned long *symbolsize,
 139                             unsigned long *offset,
 140                             char **modname, char *namebuf)
 141 {
 142         unsigned long i, low, high, mid;
 143
 144         /* This kernel should never had been booted. */
 145         BUG_ON(!kallsyms_addresses);
 146
 147         namebuf[KSYM_NAME_LEN] = 0;
 148         namebuf[0] = 0;
 149
 150         if (is_kernel_text(addr) || is_kernel_inittext(addr)) {
 151                 unsigned long symbol_end=0;
 152
 153                 /* do a binary search on the sorted kallsyms_addresses array */
 154                 low = 0;
 155                 high = kallsyms_num_syms;
 156
 157                 while (high-low > 1) {
 158                         mid = (low + high) / 2;
 159                         if (kallsyms_addresses[mid] <= addr) low = mid;
 160                         else high = mid;
 161                 }
 162
 163                 /* search for the first aliased symbol. Aliased symbols are
 164                    symbols with the same address */
 165                 while (low && kallsyms_addresses[low - 1] == kallsyms_addresses[low])
 166                         --low;
 167
 168                 /* Grab name */
 169                 kallsyms_expand_symbol(get_symbol_offset(low), namebuf);
 170
 171                 /* Search for next non-aliased symbol */
 172                 for (i = low + 1; i < kallsyms_num_syms; i++) {
 173                         if (kallsyms_addresses[i] > kallsyms_addresses[low]) {
 174                                 symbol_end = kallsyms_addresses[i];
 175                                 break;
 176                         }
 177                 }
 178
 179                 /* if we found no next symbol, we use the end of the section */
 180                 if (!symbol_end) {
 181                         if (is_kernel_inittext(addr))
 182                                 symbol_end = (unsigned long)_einittext;
 183                         else
 184                                 symbol_end = (unsigned long)_etext;
 185                 }
 186
 187                 *symbolsize = symbol_end - kallsyms_addresses[low];
 188                 *modname = NULL;
 189                 *offset = addr - kallsyms_addresses[low];
 190                 return namebuf;
 191         }
 192
 193         return module_address_lookup(addr, symbolsize, offset, modname);
 194 }
 195
 196 /* Replace "%s" in format with address, or returns -errno. */
 197 void __print_symbol(const char *fmt, unsigned long address)
 198 {
 199         char *modname;
 200         const char *name;
 201         unsigned long offset, size;
 202         char namebuf[KSYM_NAME_LEN+1];
 203         char buffer[sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +
 204                     2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1];
 205
 206         name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
 207
 208         if (!name)
 209                 sprintf(buffer, "0x%lx", address);
 210         else {
 211                 if (modname)
 212                         sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
 213                                 size, modname);
 214                 else
 215                         sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 216         }
 217         printk(fmt, buffer);
 218 }
 219
 220 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 221 struct kallsym_iter
 222 {
 223         loff_t pos;
 224         struct module *owner;
 225         unsigned long value;
 226         unsigned int nameoff; /* If iterating in core kernel symbols */
 227         char type;
 228         char name[KSYM_NAME_LEN+1];
 229 };
 230
 231 /* Only label it "global" if it is exported. */
 232 static void upcase_if_global(struct kallsym_iter *iter)
 233 {
 234         if (is_exported(iter->name, iter->owner))
 235                 iter->type += 'A' - 'a';
 236 }
 237
 238 static int get_ksymbol_mod(struct kallsym_iter *iter)
 239 {
 240         iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
 241                                          &iter->value,
 242                                          &iter->type, iter->name);
 243         if (iter->owner == NULL)
 244                 return 0;
 245
 246         upcase_if_global(iter);
 247         return 1;
 248 }
 249
 250 /* Returns space to next name. */
 251 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 252 {
 253         unsigned off = iter->nameoff;
 254
 255         iter->owner = NULL;
 256         iter->value = kallsyms_addresses[iter->pos];
 257
 258         iter->type = kallsyms_get_symbol_type(off);
 259
 260         off = kallsyms_expand_symbol(off, iter->name);
 261
 262         return off - iter->nameoff;
 263 }
 264
 265 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 266 {
 267         iter->name[0] = '\0';
 268         iter->nameoff = get_symbol_offset(new_pos);
 269         iter->pos = new_pos;
 270 }
 271
 272 /* Returns false if pos at or past end of file. */
 273 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 274 {
 275         /* Module symbols can be accessed randomly. */
 276         if (pos >= kallsyms_num_syms) {
 277                 iter->pos = pos;
 278                 return get_ksymbol_mod(iter);
 279         }
 280
 281         /* If we're not on the desired position, reset to new position. */
 282         if (pos != iter->pos)
 283                 reset_iter(iter, pos);
 284
 285         iter->nameoff += get_ksymbol_core(iter);
 286         iter->pos++;
 287
 288         return 1;
 289 }
 290
 291 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 292 {
 293         (*pos)++;
 294
 295         if (!update_iter(m->private, *pos))
 296                 return NULL;
 297         return p;
 298 }
 299
 300 static void *s_start(struct seq_file *m, loff_t *pos)
 301 {
 302         if (!update_iter(m->private, *pos))
 303                 return NULL;
 304         return m->private;
 305 }
 306
 307 static void s_stop(struct seq_file *m, void *p)
 308 {
 309 }
 310
 311 static int s_show(struct seq_file *m, void *p)
 312 {
 313         struct kallsym_iter *iter = m->private;
 314
 315         /* Some debugging symbols have no name.  Ignore them. */
 316         if (!iter->name[0])
 317                 return 0;
 318
 319         if (iter->owner)
 320                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 321                            (int)(2*sizeof(void*)),
 322                            iter->value, iter->type, iter->name,
 323                            module_name(iter->owner));
 324         else
 325                 seq_printf(m, "%0*lx %c %s\n",
 326                            (int)(2*sizeof(void*)),
 327                            iter->value, iter->type, iter->name);
 328         return 0;
 329 }
 330
 331 struct seq_operations kallsyms_op = {
 332         .start = s_start,
 333         .next = s_next,
 334         .stop = s_stop,
 335         .show = s_show
 336 };
 337
 338 static int kallsyms_open(struct inode *inode, struct file *file)
 339 {
 340         /* We keep iterator in m->private, since normal case is to
 341          * s_start from where we left off, so we avoid doing
 342          * using get_symbol_offset for every symbol */
 343         struct kallsym_iter *iter;
 344         int ret;
 345
 346         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 347         if (!iter)
 348                 return -ENOMEM;
 349         reset_iter(iter, 0);
 350
 351         ret = seq_open(file, &kallsyms_op);
 352         if (ret == 0)
 353                 ((struct seq_file *)file->private_data)->private = iter;
 354         else
 355                 kfree(iter);
 356         return ret;
 357 }
 358
 359 static int kallsyms_release(struct inode *inode, struct file *file)
 360 {
 361         struct seq_file *m = (struct seq_file *)file->private_data;
 362         kfree(m->private);
 363         return seq_release(inode, file);
 364 }
 365
 366 static struct file_operations kallsyms_operations = {
 367         .open = kallsyms_open,
 368         .read = seq_read,
 369         .llseek = seq_lseek,
 370         .release = kallsyms_release,
 371 };
 372
 373 int __init kallsyms_init(void)
 374 {
 375         struct proc_dir_entry *entry;
 376
 377         entry = create_proc_entry("kallsyms", 0444, NULL);
 378         if (entry)
 379                 entry->proc_fops = &kallsyms_operations;
 380         return 0;
 381 }
 382 __initcall(kallsyms_init);
 383
 384 EXPORT_SYMBOL(__print_symbol);