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Linux/kernel/kallsyms.c

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  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/kdb.h>
 20 #include <linux/err.h>
 21 #include <linux/proc_fs.h>
 22 #include <linux/sched.h>        /* for cond_resched */
 23 #include <linux/mm.h>
 24 #include <linux/ctype.h>
 25 #include <linux/slab.h>
 26 
 27 #include <asm/sections.h>
 28 
 29 #ifdef CONFIG_KALLSYMS_ALL
 30 #define all_var 1
 31 #else
 32 #define all_var 0
 33 #endif
 34 
 35 /*
 36  * These will be re-linked against their real values
 37  * during the second link stage.
 38  */
 39 extern const unsigned long kallsyms_addresses[] __attribute__((weak));
 40 extern const u8 kallsyms_names[] __attribute__((weak));
 41 
 42 /*
 43  * Tell the compiler that the count isn't in the small data section if the arch
 44  * has one (eg: FRV).
 45  */
 46 extern const unsigned long kallsyms_num_syms
 47 __attribute__((weak, section(".rodata")));
 48 
 49 extern const u8 kallsyms_token_table[] __attribute__((weak));
 50 extern const u16 kallsyms_token_index[] __attribute__((weak));
 51 
 52 extern const unsigned long kallsyms_markers[] __attribute__((weak));
 53 
 54 static inline int is_kernel_inittext(unsigned long addr)
 55 {
 56         if (addr >= (unsigned long)_sinittext
 57             && addr <= (unsigned long)_einittext)
 58                 return 1;
 59         return 0;
 60 }
 61 
 62 static inline int is_kernel_text(unsigned long addr)
 63 {
 64         if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
 65             arch_is_kernel_text(addr))
 66                 return 1;
 67         return in_gate_area_no_mm(addr);
 68 }
 69 
 70 static inline int is_kernel(unsigned long addr)
 71 {
 72         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
 73                 return 1;
 74         return in_gate_area_no_mm(addr);
 75 }
 76 
 77 static int is_ksym_addr(unsigned long addr)
 78 {
 79         if (all_var)
 80                 return is_kernel(addr);
 81 
 82         return is_kernel_text(addr) || is_kernel_inittext(addr);
 83 }
 84 
 85 /*
 86  * Expand a compressed symbol data into the resulting uncompressed string,
 87  * given the offset to where the symbol is in the compressed stream.
 88  */
 89 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
 90 {
 91         int len, skipped_first = 0;
 92         const u8 *tptr, *data;
 93 
 94         /* Get the compressed symbol length from the first symbol byte. */
 95         data = &kallsyms_names[off];
 96         len = *data;
 97         data++;
 98 
 99         /*
100          * Update the offset to return the offset for the next symbol on
101          * the compressed stream.
102          */
103         off += len + 1;
104 
105         /*
106          * For every byte on the compressed symbol data, copy the table
107          * entry for that byte.
108          */
109         while (len) {
110                 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
111                 data++;
112                 len--;
113 
114                 while (*tptr) {
115                         if (skipped_first) {
116                                 *result = *tptr;
117                                 result++;
118                         } else
119                                 skipped_first = 1;
120                         tptr++;
121                 }
122         }
123 
124         *result = '\0';
125 
126         /* Return to offset to the next symbol. */
127         return off;
128 }
129 
130 /*
131  * Get symbol type information. This is encoded as a single char at the
132  * beginning of the symbol name.
133  */
134 static char kallsyms_get_symbol_type(unsigned int off)
135 {
136         /*
137          * Get just the first code, look it up in the token table,
138          * and return the first char from this token.
139          */
140         return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
141 }
142 
143 
144 /*
145  * Find the offset on the compressed stream given and index in the
146  * kallsyms array.
147  */
148 static unsigned int get_symbol_offset(unsigned long pos)
149 {
150         const u8 *name;
151         int i;
152 
153         /*
154          * Use the closest marker we have. We have markers every 256 positions,
155          * so that should be close enough.
156          */
157         name = &kallsyms_names[kallsyms_markers[pos >> 8]];
158 
159         /*
160          * Sequentially scan all the symbols up to the point we're searching
161          * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
162          * so we just need to add the len to the current pointer for every
163          * symbol we wish to skip.
164          */
165         for (i = 0; i < (pos & 0xFF); i++)
166                 name = name + (*name) + 1;
167 
168         return name - kallsyms_names;
169 }
170 
171 /* Lookup the address for this symbol. Returns 0 if not found. */
172 unsigned long kallsyms_lookup_name(const char *name)
173 {
174         char namebuf[KSYM_NAME_LEN];
175         unsigned long i;
176         unsigned int off;
177 
178         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
179                 off = kallsyms_expand_symbol(off, namebuf);
180 
181                 if (strcmp(namebuf, name) == 0)
182                         return kallsyms_addresses[i];
183         }
184         return module_kallsyms_lookup_name(name);
185 }
186 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
187 
188 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
189                                       unsigned long),
190                             void *data)
191 {
192         char namebuf[KSYM_NAME_LEN];
193         unsigned long i;
194         unsigned int off;
195         int ret;
196 
197         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
198                 off = kallsyms_expand_symbol(off, namebuf);
199                 ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
200                 if (ret != 0)
201                         return ret;
202         }
203         return module_kallsyms_on_each_symbol(fn, data);
204 }
205 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
206 
207 static unsigned long get_symbol_pos(unsigned long addr,
208                                     unsigned long *symbolsize,
209                                     unsigned long *offset)
210 {
211         unsigned long symbol_start = 0, symbol_end = 0;
212         unsigned long i, low, high, mid;
213 
214         /* This kernel should never had been booted. */
215         BUG_ON(!kallsyms_addresses);
216 
217         /* Do a binary search on the sorted kallsyms_addresses array. */
218         low = 0;
219         high = kallsyms_num_syms;
220 
221         while (high - low > 1) {
222                 mid = low + (high - low) / 2;
223                 if (kallsyms_addresses[mid] <= addr)
224                         low = mid;
225                 else
226                         high = mid;
227         }
228 
229         /*
230          * Search for the first aliased symbol. Aliased
231          * symbols are symbols with the same address.
232          */
233         while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
234                 --low;
235 
236         symbol_start = kallsyms_addresses[low];
237 
238         /* Search for next non-aliased symbol. */
239         for (i = low + 1; i < kallsyms_num_syms; i++) {
240                 if (kallsyms_addresses[i] > symbol_start) {
241                         symbol_end = kallsyms_addresses[i];
242                         break;
243                 }
244         }
245 
246         /* If we found no next symbol, we use the end of the section. */
247         if (!symbol_end) {
248                 if (is_kernel_inittext(addr))
249                         symbol_end = (unsigned long)_einittext;
250                 else if (all_var)
251                         symbol_end = (unsigned long)_end;
252                 else
253                         symbol_end = (unsigned long)_etext;
254         }
255 
256         if (symbolsize)
257                 *symbolsize = symbol_end - symbol_start;
258         if (offset)
259                 *offset = addr - symbol_start;
260 
261         return low;
262 }
263 
264 /*
265  * Lookup an address but don't bother to find any names.
266  */
267 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
268                                 unsigned long *offset)
269 {
270         char namebuf[KSYM_NAME_LEN];
271         if (is_ksym_addr(addr))
272                 return !!get_symbol_pos(addr, symbolsize, offset);
273 
274         return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
275 }
276 
277 /*
278  * Lookup an address
279  * - modname is set to NULL if it's in the kernel.
280  * - We guarantee that the returned name is valid until we reschedule even if.
281  *   It resides in a module.
282  * - We also guarantee that modname will be valid until rescheduled.
283  */
284 const char *kallsyms_lookup(unsigned long addr,
285                             unsigned long *symbolsize,
286                             unsigned long *offset,
287                             char **modname, char *namebuf)
288 {
289         namebuf[KSYM_NAME_LEN - 1] = 0;
290         namebuf[0] = 0;
291 
292         if (is_ksym_addr(addr)) {
293                 unsigned long pos;
294 
295                 pos = get_symbol_pos(addr, symbolsize, offset);
296                 /* Grab name */
297                 kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
298                 if (modname)
299                         *modname = NULL;
300                 return namebuf;
301         }
302 
303         /* See if it's in a module. */
304         return module_address_lookup(addr, symbolsize, offset, modname,
305                                      namebuf);
306 }
307 
308 int lookup_symbol_name(unsigned long addr, char *symname)
309 {
310         symname[0] = '\0';
311         symname[KSYM_NAME_LEN - 1] = '\0';
312 
313         if (is_ksym_addr(addr)) {
314                 unsigned long pos;
315 
316                 pos = get_symbol_pos(addr, NULL, NULL);
317                 /* Grab name */
318                 kallsyms_expand_symbol(get_symbol_offset(pos), symname);
319                 return 0;
320         }
321         /* See if it's in a module. */
322         return lookup_module_symbol_name(addr, symname);
323 }
324 
325 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
326                         unsigned long *offset, char *modname, char *name)
327 {
328         name[0] = '\0';
329         name[KSYM_NAME_LEN - 1] = '\0';
330 
331         if (is_ksym_addr(addr)) {
332                 unsigned long pos;
333 
334                 pos = get_symbol_pos(addr, size, offset);
335                 /* Grab name */
336                 kallsyms_expand_symbol(get_symbol_offset(pos), name);
337                 modname[0] = '\0';
338                 return 0;
339         }
340         /* See if it's in a module. */
341         return lookup_module_symbol_attrs(addr, size, offset, modname, name);
342 }
343 
344 /* Look up a kernel symbol and return it in a text buffer. */
345 static int __sprint_symbol(char *buffer, unsigned long address,
346                            int symbol_offset, int add_offset)
347 {
348         char *modname;
349         const char *name;
350         unsigned long offset, size;
351         int len;
352 
353         address += symbol_offset;
354         name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
355         if (!name)
356                 return sprintf(buffer, "0x%lx", address);
357 
358         if (name != buffer)
359                 strcpy(buffer, name);
360         len = strlen(buffer);
361         offset -= symbol_offset;
362 
363         if (add_offset)
364                 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
365 
366         if (modname)
367                 len += sprintf(buffer + len, " [%s]", modname);
368 
369         return len;
370 }
371 
372 /**
373  * sprint_symbol - Look up a kernel symbol and return it in a text buffer
374  * @buffer: buffer to be stored
375  * @address: address to lookup
376  *
377  * This function looks up a kernel symbol with @address and stores its name,
378  * offset, size and module name to @buffer if possible. If no symbol was found,
379  * just saves its @address as is.
380  *
381  * This function returns the number of bytes stored in @buffer.
382  */
383 int sprint_symbol(char *buffer, unsigned long address)
384 {
385         return __sprint_symbol(buffer, address, 0, 1);
386 }
387 EXPORT_SYMBOL_GPL(sprint_symbol);
388 
389 /**
390  * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
391  * @buffer: buffer to be stored
392  * @address: address to lookup
393  *
394  * This function looks up a kernel symbol with @address and stores its name
395  * and module name to @buffer if possible. If no symbol was found, just saves
396  * its @address as is.
397  *
398  * This function returns the number of bytes stored in @buffer.
399  */
400 int sprint_symbol_no_offset(char *buffer, unsigned long address)
401 {
402         return __sprint_symbol(buffer, address, 0, 0);
403 }
404 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
405 
406 /**
407  * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
408  * @buffer: buffer to be stored
409  * @address: address to lookup
410  *
411  * This function is for stack backtrace and does the same thing as
412  * sprint_symbol() but with modified/decreased @address. If there is a
413  * tail-call to the function marked "noreturn", gcc optimized out code after
414  * the call so that the stack-saved return address could point outside of the
415  * caller. This function ensures that kallsyms will find the original caller
416  * by decreasing @address.
417  *
418  * This function returns the number of bytes stored in @buffer.
419  */
420 int sprint_backtrace(char *buffer, unsigned long address)
421 {
422         return __sprint_symbol(buffer, address, -1, 1);
423 }
424 
425 /* Look up a kernel symbol and print it to the kernel messages. */
426 void __print_symbol(const char *fmt, unsigned long address)
427 {
428         char buffer[KSYM_SYMBOL_LEN];
429 
430         sprint_symbol(buffer, address);
431 
432         printk(fmt, buffer);
433 }
434 EXPORT_SYMBOL(__print_symbol);
435 
436 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
437 struct kallsym_iter {
438         loff_t pos;
439         unsigned long value;
440         unsigned int nameoff; /* If iterating in core kernel symbols. */
441         char type;
442         char name[KSYM_NAME_LEN];
443         char module_name[MODULE_NAME_LEN];
444         int exported;
445 };
446 
447 static int get_ksymbol_mod(struct kallsym_iter *iter)
448 {
449         if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
450                                 &iter->type, iter->name, iter->module_name,
451                                 &iter->exported) < 0)
452                 return 0;
453         return 1;
454 }
455 
456 /* Returns space to next name. */
457 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
458 {
459         unsigned off = iter->nameoff;
460 
461         iter->module_name[0] = '\0';
462         iter->value = kallsyms_addresses[iter->pos];
463 
464         iter->type = kallsyms_get_symbol_type(off);
465 
466         off = kallsyms_expand_symbol(off, iter->name);
467 
468         return off - iter->nameoff;
469 }
470 
471 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
472 {
473         iter->name[0] = '\0';
474         iter->nameoff = get_symbol_offset(new_pos);
475         iter->pos = new_pos;
476 }
477 
478 /* Returns false if pos at or past end of file. */
479 static int update_iter(struct kallsym_iter *iter, loff_t pos)
480 {
481         /* Module symbols can be accessed randomly. */
482         if (pos >= kallsyms_num_syms) {
483                 iter->pos = pos;
484                 return get_ksymbol_mod(iter);
485         }
486 
487         /* If we're not on the desired position, reset to new position. */
488         if (pos != iter->pos)
489                 reset_iter(iter, pos);
490 
491         iter->nameoff += get_ksymbol_core(iter);
492         iter->pos++;
493 
494         return 1;
495 }
496 
497 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
498 {
499         (*pos)++;
500 
501         if (!update_iter(m->private, *pos))
502                 return NULL;
503         return p;
504 }
505 
506 static void *s_start(struct seq_file *m, loff_t *pos)
507 {
508         if (!update_iter(m->private, *pos))
509                 return NULL;
510         return m->private;
511 }
512 
513 static void s_stop(struct seq_file *m, void *p)
514 {
515 }
516 
517 static int s_show(struct seq_file *m, void *p)
518 {
519         struct kallsym_iter *iter = m->private;
520 
521         /* Some debugging symbols have no name.  Ignore them. */
522         if (!iter->name[0])
523                 return 0;
524 
525         if (iter->module_name[0]) {
526                 char type;
527 
528                 /*
529                  * Label it "global" if it is exported,
530                  * "local" if not exported.
531                  */
532                 type = iter->exported ? toupper(iter->type) :
533                                         tolower(iter->type);
534                 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
535                            type, iter->name, iter->module_name);
536         } else
537                 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
538                            iter->type, iter->name);
539         return 0;
540 }
541 
542 static const struct seq_operations kallsyms_op = {
543         .start = s_start,
544         .next = s_next,
545         .stop = s_stop,
546         .show = s_show
547 };
548 
549 static int kallsyms_open(struct inode *inode, struct file *file)
550 {
551         /*
552          * We keep iterator in m->private, since normal case is to
553          * s_start from where we left off, so we avoid doing
554          * using get_symbol_offset for every symbol.
555          */
556         struct kallsym_iter *iter;
557         int ret;
558 
559         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
560         if (!iter)
561                 return -ENOMEM;
562         reset_iter(iter, 0);
563 
564         ret = seq_open(file, &kallsyms_op);
565         if (ret == 0)
566                 ((struct seq_file *)file->private_data)->private = iter;
567         else
568                 kfree(iter);
569         return ret;
570 }
571 
572 #ifdef  CONFIG_KGDB_KDB
573 const char *kdb_walk_kallsyms(loff_t *pos)
574 {
575         static struct kallsym_iter kdb_walk_kallsyms_iter;
576         if (*pos == 0) {
577                 memset(&kdb_walk_kallsyms_iter, 0,
578                        sizeof(kdb_walk_kallsyms_iter));
579                 reset_iter(&kdb_walk_kallsyms_iter, 0);
580         }
581         while (1) {
582                 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
583                         return NULL;
584                 ++*pos;
585                 /* Some debugging symbols have no name.  Ignore them. */
586                 if (kdb_walk_kallsyms_iter.name[0])
587                         return kdb_walk_kallsyms_iter.name;
588         }
589 }
590 #endif  /* CONFIG_KGDB_KDB */
591 
592 static const struct file_operations kallsyms_operations = {
593         .open = kallsyms_open,
594         .read = seq_read,
595         .llseek = seq_lseek,
596         .release = seq_release_private,
597 };
598 
599 static int __init kallsyms_init(void)
600 {
601         proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
602         return 0;
603 }
604 device_initcall(kallsyms_init);
605 

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