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/mm.h>
  22
  23 #include <asm/sections.h>
  24
  25 #ifdef CONFIG_KALLSYMS_ALL
  26 #define all_var 1
  27 #else
  28 #define all_var 0
  29 #endif
  30
  31 /* These will be re-linked against their real values during the second link stage */
  32 extern unsigned long kallsyms_addresses[] __attribute__((weak));
  33 extern unsigned long kallsyms_num_syms __attribute__((weak,section("data")));
  34 extern u8 kallsyms_names[] __attribute__((weak));
  35
  36 extern u8 kallsyms_token_table[] __attribute__((weak));
  37 extern u16 kallsyms_token_index[] __attribute__((weak));
  38
  39 extern unsigned long kallsyms_markers[] __attribute__((weak));
  40
  41 static inline int is_kernel_inittext(unsigned long addr)
  42 {
  43         if (addr >= (unsigned long)_sinittext
  44             && addr <= (unsigned long)_einittext)
  45                 return 1;
  46         return 0;
  47 }
  48
  49 static inline int is_kernel_text(unsigned long addr)
  50 {
  51         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
  52                 return 1;
  53         return in_gate_area_no_task(addr);
  54 }
  55
  56 static inline int is_kernel(unsigned long addr)
  57 {
  58         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
  59                 return 1;
  60         return in_gate_area_no_task(addr);
  61 }
  62
  63 /* expand a compressed symbol data into the resulting uncompressed string,
  64    given the offset to where the symbol is in the compressed stream */
  65 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
  66 {
  67         int len, skipped_first = 0;
  68         u8 *tptr, *data;
  69
  70         /* get the compressed symbol length from the first symbol byte */
  71         data = &kallsyms_names[off];
  72         len = *data;
  73         data++;
  74
  75         /* update the offset to return the offset for the next symbol on
  76          * the compressed stream */
  77         off += len + 1;
  78
  79         /* for every byte on the compressed symbol data, copy the table
  80            entry for that byte */
  81         while(len) {
  82                 tptr = &kallsyms_token_table[ kallsyms_token_index[*data] ];
  83                 data++;
  84                 len--;
  85
  86                 while (*tptr) {
  87                         if(skipped_first) {
  88                                 *result = *tptr;
  89                                 result++;
  90                         } else
  91                                 skipped_first = 1;
  92                         tptr++;
  93                 }
  94         }
  95
  96         *result = '\0';
  97
  98         /* return to offset to the next symbol */
  99         return off;
 100 }
 101
 102 /* get symbol type information. This is encoded as a single char at the
 103  * begining of the symbol name */
 104 static char kallsyms_get_symbol_type(unsigned int off)
 105 {
 106         /* get just the first code, look it up in the token table, and return the
 107          * first char from this token */
 108         return kallsyms_token_table[ kallsyms_token_index[ kallsyms_names[off+1] ] ];
 109 }
 110
 111
 112 /* find the offset on the compressed stream given and index in the
 113  * kallsyms array */
 114 static unsigned int get_symbol_offset(unsigned long pos)
 115 {
 116         u8 *name;
 117         int i;
 118
 119         /* use the closest marker we have. We have markers every 256 positions,
 120          * so that should be close enough */
 121         name = &kallsyms_names[ kallsyms_markers[pos>>8] ];
 122
 123         /* sequentially scan all the symbols up to the point we're searching for.
 124          * Every symbol is stored in a [<len>][<len> bytes of data] format, so we
 125          * just need to add the len to the current pointer for every symbol we
 126          * wish to skip */
 127         for(i = 0; i < (pos&0xFF); i++)
 128                 name = name + (*name) + 1;
 129
 130         return name - kallsyms_names;
 131 }
 132
 133 /* Lookup the address for this symbol. Returns 0 if not found. */
 134 unsigned long kallsyms_lookup_name(const char *name)
 135 {
 136         char namebuf[KSYM_NAME_LEN+1];
 137         unsigned long i;
 138         unsigned int off;
 139
 140         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 141                 off = kallsyms_expand_symbol(off, namebuf);
 142
 143                 if (strcmp(namebuf, name) == 0)
 144                         return kallsyms_addresses[i];
 145         }
 146         return module_kallsyms_lookup_name(name);
 147 }
 148 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
 149
 150 /*
 151  * Lookup an address
 152  * - modname is set to NULL if it's in the kernel
 153  * - we guarantee that the returned name is valid until we reschedule even if
 154  *   it resides in a module
 155  * - we also guarantee that modname will be valid until rescheduled
 156  */
 157 const char *kallsyms_lookup(unsigned long addr,
 158                             unsigned long *symbolsize,
 159                             unsigned long *offset,
 160                             char **modname, char *namebuf)
 161 {
 162         unsigned long i, low, high, mid;
 163         const char *msym;
 164
 165         /* This kernel should never had been booted. */
 166         BUG_ON(!kallsyms_addresses);
 167
 168         namebuf[KSYM_NAME_LEN] = 0;
 169         namebuf[0] = 0;
 170
 171         if ((all_var && is_kernel(addr)) ||
 172             (!all_var && (is_kernel_text(addr) || is_kernel_inittext(addr)))) {
 173                 unsigned long symbol_end=0;
 174
 175                 /* do a binary search on the sorted kallsyms_addresses array */
 176                 low = 0;
 177                 high = kallsyms_num_syms;
 178
 179                 while (high-low > 1) {
 180                         mid = (low + high) / 2;
 181                         if (kallsyms_addresses[mid] <= addr) low = mid;
 182                         else high = mid;
 183                 }
 184
 185                 /* search for the first aliased symbol. Aliased symbols are
 186                    symbols with the same address */
 187                 while (low && kallsyms_addresses[low - 1] == kallsyms_addresses[low])
 188                         --low;
 189
 190                 /* Grab name */
 191                 kallsyms_expand_symbol(get_symbol_offset(low), namebuf);
 192
 193                 /* Search for next non-aliased symbol */
 194                 for (i = low + 1; i < kallsyms_num_syms; i++) {
 195                         if (kallsyms_addresses[i] > kallsyms_addresses[low]) {
 196                                 symbol_end = kallsyms_addresses[i];
 197                                 break;
 198                         }
 199                 }
 200
 201                 /* if we found no next symbol, we use the end of the section */
 202                 if (!symbol_end) {
 203                         if (is_kernel_inittext(addr))
 204                                 symbol_end = (unsigned long)_einittext;
 205                         else
 206                                 symbol_end = all_var ? (unsigned long)_end : (unsigned long)_etext;
 207                 }
 208
 209                 *symbolsize = symbol_end - kallsyms_addresses[low];
 210                 *modname = NULL;
 211                 *offset = addr - kallsyms_addresses[low];
 212                 return namebuf;
 213         }
 214
 215         /* see if it's in a module */
 216         msym = module_address_lookup(addr, symbolsize, offset, modname);
 217         if (msym)
 218                 return strncpy(namebuf, msym, KSYM_NAME_LEN);
 219
 220         return NULL;
 221 }
 222
 223 /* Replace "%s" in format with address, or returns -errno. */
 224 void __print_symbol(const char *fmt, unsigned long address)
 225 {
 226         char *modname;
 227         const char *name;
 228         unsigned long offset, size;
 229         char namebuf[KSYM_NAME_LEN+1];
 230         char buffer[sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +
 231                     2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1];
 232
 233         name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
 234
 235         if (!name)
 236                 sprintf(buffer, "0x%lx", address);
 237         else {
 238                 if (modname)
 239                         sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
 240                                 size, modname);
 241                 else
 242                         sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 243         }
 244         printk(fmt, buffer);
 245 }
 246
 247 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 248 struct kallsym_iter
 249 {
 250         loff_t pos;
 251         struct module *owner;
 252         unsigned long value;
 253         unsigned int nameoff; /* If iterating in core kernel symbols */
 254         char type;
 255         char name[KSYM_NAME_LEN+1];
 256 };
 257
 258 /* Only label it "global" if it is exported. */
 259 static void upcase_if_global(struct kallsym_iter *iter)
 260 {
 261         if (is_exported(iter->name, iter->owner))
 262                 iter->type += 'A' - 'a';
 263 }
 264
 265 static int get_ksymbol_mod(struct kallsym_iter *iter)
 266 {
 267         iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
 268                                          &iter->value,
 269                                          &iter->type, iter->name);
 270         if (iter->owner == NULL)
 271                 return 0;
 272
 273         upcase_if_global(iter);
 274         return 1;
 275 }
 276
 277 /* Returns space to next name. */
 278 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 279 {
 280         unsigned off = iter->nameoff;
 281
 282         iter->owner = NULL;
 283         iter->value = kallsyms_addresses[iter->pos];
 284
 285         iter->type = kallsyms_get_symbol_type(off);
 286
 287         off = kallsyms_expand_symbol(off, iter->name);
 288
 289         return off - iter->nameoff;
 290 }
 291
 292 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 293 {
 294         iter->name[0] = '\0';
 295         iter->nameoff = get_symbol_offset(new_pos);
 296         iter->pos = new_pos;
 297 }
 298
 299 /* Returns false if pos at or past end of file. */
 300 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 301 {
 302         /* Module symbols can be accessed randomly. */
 303         if (pos >= kallsyms_num_syms) {
 304                 iter->pos = pos;
 305                 return get_ksymbol_mod(iter);
 306         }
 307
 308         /* If we're not on the desired position, reset to new position. */
 309         if (pos != iter->pos)
 310                 reset_iter(iter, pos);
 311
 312         iter->nameoff += get_ksymbol_core(iter);
 313         iter->pos++;
 314
 315         return 1;
 316 }
 317
 318 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 319 {
 320         (*pos)++;
 321
 322         if (!update_iter(m->private, *pos))
 323                 return NULL;
 324         return p;
 325 }
 326
 327 static void *s_start(struct seq_file *m, loff_t *pos)
 328 {
 329         if (!update_iter(m->private, *pos))
 330                 return NULL;
 331         return m->private;
 332 }
 333
 334 static void s_stop(struct seq_file *m, void *p)
 335 {
 336 }
 337
 338 static int s_show(struct seq_file *m, void *p)
 339 {
 340         struct kallsym_iter *iter = m->private;
 341
 342         /* Some debugging symbols have no name.  Ignore them. */
 343         if (!iter->name[0])
 344                 return 0;
 345
 346         if (iter->owner)
 347                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 348                            (int)(2*sizeof(void*)),
 349                            iter->value, iter->type, iter->name,
 350                            module_name(iter->owner));
 351         else
 352                 seq_printf(m, "%0*lx %c %s\n",
 353                            (int)(2*sizeof(void*)),
 354                            iter->value, iter->type, iter->name);
 355         return 0;
 356 }
 357
 358 static struct seq_operations kallsyms_op = {
 359         .start = s_start,
 360         .next = s_next,
 361         .stop = s_stop,
 362         .show = s_show
 363 };
 364
 365 static int kallsyms_open(struct inode *inode, struct file *file)
 366 {
 367         /* We keep iterator in m->private, since normal case is to
 368          * s_start from where we left off, so we avoid doing
 369          * using get_symbol_offset for every symbol */
 370         struct kallsym_iter *iter;
 371         int ret;
 372
 373         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 374         if (!iter)
 375                 return -ENOMEM;
 376         reset_iter(iter, 0);
 377
 378         ret = seq_open(file, &kallsyms_op);
 379         if (ret == 0)
 380                 ((struct seq_file *)file->private_data)->private = iter;
 381         else
 382                 kfree(iter);
 383         return ret;
 384 }
 385
 386 static int kallsyms_release(struct inode *inode, struct file *file)
 387 {
 388         struct seq_file *m = (struct seq_file *)file->private_data;
 389         kfree(m->private);
 390         return seq_release(inode, file);
 391 }
 392
 393 static struct file_operations kallsyms_operations = {
 394         .open = kallsyms_open,
 395         .read = seq_read,
 396         .llseek = seq_lseek,
 397         .release = kallsyms_release,
 398 };
 399
 400 static int __init kallsyms_init(void)
 401 {
 402         struct proc_dir_entry *entry;
 403
 404         entry = create_proc_entry("kallsyms", 0444, NULL);
 405         if (entry)
 406                 entry->proc_fops = &kallsyms_operations;
 407         return 0;
 408 }
 409 __initcall(kallsyms_init);
 410
 411 EXPORT_SYMBOL(__print_symbol);