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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 #include <linux/compiler.h>
 27 
 28 #include <asm/sections.h>
 29 
 30 #ifdef CONFIG_KALLSYMS_ALL
 31 #define all_var 1
 32 #else
 33 #define all_var 0
 34 #endif
 35 
 36 /*
 37  * These will be re-linked against their real values
 38  * during the second link stage.
 39  */
 40 extern const unsigned long kallsyms_addresses[] __weak;
 41 extern const u8 kallsyms_names[] __weak;
 42 
 43 /*
 44  * Tell the compiler that the count isn't in the small data section if the arch
 45  * has one (eg: FRV).
 46  */
 47 extern const unsigned long kallsyms_num_syms
 48 __attribute__((weak, section(".rodata")));
 49 
 50 extern const u8 kallsyms_token_table[] __weak;
 51 extern const u16 kallsyms_token_index[] __weak;
 52 
 53 extern const unsigned long kallsyms_markers[] __weak;
 54 
 55 static inline int is_kernel_inittext(unsigned long addr)
 56 {
 57         if (addr >= (unsigned long)_sinittext
 58             && addr <= (unsigned long)_einittext)
 59                 return 1;
 60         return 0;
 61 }
 62 
 63 static inline int is_kernel_text(unsigned long addr)
 64 {
 65         if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
 66             arch_is_kernel_text(addr))
 67                 return 1;
 68         return in_gate_area_no_mm(addr);
 69 }
 70 
 71 static inline int is_kernel(unsigned long addr)
 72 {
 73         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
 74                 return 1;
 75         return in_gate_area_no_mm(addr);
 76 }
 77 
 78 static int is_ksym_addr(unsigned long addr)
 79 {
 80         if (all_var)
 81                 return is_kernel(addr);
 82 
 83         return is_kernel_text(addr) || is_kernel_inittext(addr);
 84 }
 85 
 86 /*
 87  * Expand a compressed symbol data into the resulting uncompressed string,
 88  * if uncompressed string is too long (>= maxlen), it will be truncated,
 89  * given the offset to where the symbol is in the compressed stream.
 90  */
 91 static unsigned int kallsyms_expand_symbol(unsigned int off,
 92                                            char *result, size_t maxlen)
 93 {
 94         int len, skipped_first = 0;
 95         const u8 *tptr, *data;
 96 
 97         /* Get the compressed symbol length from the first symbol byte. */
 98         data = &kallsyms_names[off];
 99         len = *data;
100         data++;
101 
102         /*
103          * Update the offset to return the offset for the next symbol on
104          * the compressed stream.
105          */
106         off += len + 1;
107 
108         /*
109          * For every byte on the compressed symbol data, copy the table
110          * entry for that byte.
111          */
112         while (len) {
113                 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
114                 data++;
115                 len--;
116 
117                 while (*tptr) {
118                         if (skipped_first) {
119                                 if (maxlen <= 1)
120                                         goto tail;
121                                 *result = *tptr;
122                                 result++;
123                                 maxlen--;
124                         } else
125                                 skipped_first = 1;
126                         tptr++;
127                 }
128         }
129 
130 tail:
131         if (maxlen)
132                 *result = '\0';
133 
134         /* Return to offset to the next symbol. */
135         return off;
136 }
137 
138 /*
139  * Get symbol type information. This is encoded as a single char at the
140  * beginning of the symbol name.
141  */
142 static char kallsyms_get_symbol_type(unsigned int off)
143 {
144         /*
145          * Get just the first code, look it up in the token table,
146          * and return the first char from this token.
147          */
148         return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
149 }
150 
151 
152 /*
153  * Find the offset on the compressed stream given and index in the
154  * kallsyms array.
155  */
156 static unsigned int get_symbol_offset(unsigned long pos)
157 {
158         const u8 *name;
159         int i;
160 
161         /*
162          * Use the closest marker we have. We have markers every 256 positions,
163          * so that should be close enough.
164          */
165         name = &kallsyms_names[kallsyms_markers[pos >> 8]];
166 
167         /*
168          * Sequentially scan all the symbols up to the point we're searching
169          * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
170          * so we just need to add the len to the current pointer for every
171          * symbol we wish to skip.
172          */
173         for (i = 0; i < (pos & 0xFF); i++)
174                 name = name + (*name) + 1;
175 
176         return name - kallsyms_names;
177 }
178 
179 /* Lookup the address for this symbol. Returns 0 if not found. */
180 unsigned long kallsyms_lookup_name(const char *name)
181 {
182         char namebuf[KSYM_NAME_LEN];
183         unsigned long i;
184         unsigned int off;
185 
186         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
187                 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
188 
189                 if (strcmp(namebuf, name) == 0)
190                         return kallsyms_addresses[i];
191         }
192         return module_kallsyms_lookup_name(name);
193 }
194 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
195 
196 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
197                                       unsigned long),
198                             void *data)
199 {
200         char namebuf[KSYM_NAME_LEN];
201         unsigned long i;
202         unsigned int off;
203         int ret;
204 
205         for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
206                 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
207                 ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
208                 if (ret != 0)
209                         return ret;
210         }
211         return module_kallsyms_on_each_symbol(fn, data);
212 }
213 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
214 
215 static unsigned long get_symbol_pos(unsigned long addr,
216                                     unsigned long *symbolsize,
217                                     unsigned long *offset)
218 {
219         unsigned long symbol_start = 0, symbol_end = 0;
220         unsigned long i, low, high, mid;
221 
222         /* This kernel should never had been booted. */
223         BUG_ON(!kallsyms_addresses);
224 
225         /* Do a binary search on the sorted kallsyms_addresses array. */
226         low = 0;
227         high = kallsyms_num_syms;
228 
229         while (high - low > 1) {
230                 mid = low + (high - low) / 2;
231                 if (kallsyms_addresses[mid] <= addr)
232                         low = mid;
233                 else
234                         high = mid;
235         }
236 
237         /*
238          * Search for the first aliased symbol. Aliased
239          * symbols are symbols with the same address.
240          */
241         while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
242                 --low;
243 
244         symbol_start = kallsyms_addresses[low];
245 
246         /* Search for next non-aliased symbol. */
247         for (i = low + 1; i < kallsyms_num_syms; i++) {
248                 if (kallsyms_addresses[i] > symbol_start) {
249                         symbol_end = kallsyms_addresses[i];
250                         break;
251                 }
252         }
253 
254         /* If we found no next symbol, we use the end of the section. */
255         if (!symbol_end) {
256                 if (is_kernel_inittext(addr))
257                         symbol_end = (unsigned long)_einittext;
258                 else if (all_var)
259                         symbol_end = (unsigned long)_end;
260                 else
261                         symbol_end = (unsigned long)_etext;
262         }
263 
264         if (symbolsize)
265                 *symbolsize = symbol_end - symbol_start;
266         if (offset)
267                 *offset = addr - symbol_start;
268 
269         return low;
270 }
271 
272 /*
273  * Lookup an address but don't bother to find any names.
274  */
275 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
276                                 unsigned long *offset)
277 {
278         char namebuf[KSYM_NAME_LEN];
279         if (is_ksym_addr(addr))
280                 return !!get_symbol_pos(addr, symbolsize, offset);
281 
282         return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
283 }
284 
285 /*
286  * Lookup an address
287  * - modname is set to NULL if it's in the kernel.
288  * - We guarantee that the returned name is valid until we reschedule even if.
289  *   It resides in a module.
290  * - We also guarantee that modname will be valid until rescheduled.
291  */
292 const char *kallsyms_lookup(unsigned long addr,
293                             unsigned long *symbolsize,
294                             unsigned long *offset,
295                             char **modname, char *namebuf)
296 {
297         namebuf[KSYM_NAME_LEN - 1] = 0;
298         namebuf[0] = 0;
299 
300         if (is_ksym_addr(addr)) {
301                 unsigned long pos;
302 
303                 pos = get_symbol_pos(addr, symbolsize, offset);
304                 /* Grab name */
305                 kallsyms_expand_symbol(get_symbol_offset(pos),
306                                        namebuf, KSYM_NAME_LEN);
307                 if (modname)
308                         *modname = NULL;
309                 return namebuf;
310         }
311 
312         /* See if it's in a module. */
313         return module_address_lookup(addr, symbolsize, offset, modname,
314                                      namebuf);
315 }
316 
317 int lookup_symbol_name(unsigned long addr, char *symname)
318 {
319         symname[0] = '\0';
320         symname[KSYM_NAME_LEN - 1] = '\0';
321 
322         if (is_ksym_addr(addr)) {
323                 unsigned long pos;
324 
325                 pos = get_symbol_pos(addr, NULL, NULL);
326                 /* Grab name */
327                 kallsyms_expand_symbol(get_symbol_offset(pos),
328                                        symname, KSYM_NAME_LEN);
329                 return 0;
330         }
331         /* See if it's in a module. */
332         return lookup_module_symbol_name(addr, symname);
333 }
334 
335 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
336                         unsigned long *offset, char *modname, char *name)
337 {
338         name[0] = '\0';
339         name[KSYM_NAME_LEN - 1] = '\0';
340 
341         if (is_ksym_addr(addr)) {
342                 unsigned long pos;
343 
344                 pos = get_symbol_pos(addr, size, offset);
345                 /* Grab name */
346                 kallsyms_expand_symbol(get_symbol_offset(pos),
347                                        name, KSYM_NAME_LEN);
348                 modname[0] = '\0';
349                 return 0;
350         }
351         /* See if it's in a module. */
352         return lookup_module_symbol_attrs(addr, size, offset, modname, name);
353 }
354 
355 /* Look up a kernel symbol and return it in a text buffer. */
356 static int __sprint_symbol(char *buffer, unsigned long address,
357                            int symbol_offset, int add_offset)
358 {
359         char *modname;
360         const char *name;
361         unsigned long offset, size;
362         int len;
363 
364         address += symbol_offset;
365         name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
366         if (!name)
367                 return sprintf(buffer, "0x%lx", address);
368 
369         if (name != buffer)
370                 strcpy(buffer, name);
371         len = strlen(buffer);
372         offset -= symbol_offset;
373 
374         if (add_offset)
375                 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
376 
377         if (modname)
378                 len += sprintf(buffer + len, " [%s]", modname);
379 
380         return len;
381 }
382 
383 /**
384  * sprint_symbol - Look up a kernel symbol and return it in a text buffer
385  * @buffer: buffer to be stored
386  * @address: address to lookup
387  *
388  * This function looks up a kernel symbol with @address and stores its name,
389  * offset, size and module name to @buffer if possible. If no symbol was found,
390  * just saves its @address as is.
391  *
392  * This function returns the number of bytes stored in @buffer.
393  */
394 int sprint_symbol(char *buffer, unsigned long address)
395 {
396         return __sprint_symbol(buffer, address, 0, 1);
397 }
398 EXPORT_SYMBOL_GPL(sprint_symbol);
399 
400 /**
401  * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
402  * @buffer: buffer to be stored
403  * @address: address to lookup
404  *
405  * This function looks up a kernel symbol with @address and stores its name
406  * and module name to @buffer if possible. If no symbol was found, just saves
407  * its @address as is.
408  *
409  * This function returns the number of bytes stored in @buffer.
410  */
411 int sprint_symbol_no_offset(char *buffer, unsigned long address)
412 {
413         return __sprint_symbol(buffer, address, 0, 0);
414 }
415 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
416 
417 /**
418  * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
419  * @buffer: buffer to be stored
420  * @address: address to lookup
421  *
422  * This function is for stack backtrace and does the same thing as
423  * sprint_symbol() but with modified/decreased @address. If there is a
424  * tail-call to the function marked "noreturn", gcc optimized out code after
425  * the call so that the stack-saved return address could point outside of the
426  * caller. This function ensures that kallsyms will find the original caller
427  * by decreasing @address.
428  *
429  * This function returns the number of bytes stored in @buffer.
430  */
431 int sprint_backtrace(char *buffer, unsigned long address)
432 {
433         return __sprint_symbol(buffer, address, -1, 1);
434 }
435 
436 /* Look up a kernel symbol and print it to the kernel messages. */
437 void __print_symbol(const char *fmt, unsigned long address)
438 {
439         char buffer[KSYM_SYMBOL_LEN];
440 
441         sprint_symbol(buffer, address);
442 
443         printk(fmt, buffer);
444 }
445 EXPORT_SYMBOL(__print_symbol);
446 
447 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
448 struct kallsym_iter {
449         loff_t pos;
450         unsigned long value;
451         unsigned int nameoff; /* If iterating in core kernel symbols. */
452         char type;
453         char name[KSYM_NAME_LEN];
454         char module_name[MODULE_NAME_LEN];
455         int exported;
456 };
457 
458 static int get_ksymbol_mod(struct kallsym_iter *iter)
459 {
460         if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
461                                 &iter->type, iter->name, iter->module_name,
462                                 &iter->exported) < 0)
463                 return 0;
464         return 1;
465 }
466 
467 /* Returns space to next name. */
468 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
469 {
470         unsigned off = iter->nameoff;
471 
472         iter->module_name[0] = '\0';
473         iter->value = kallsyms_addresses[iter->pos];
474 
475         iter->type = kallsyms_get_symbol_type(off);
476 
477         off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
478 
479         return off - iter->nameoff;
480 }
481 
482 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
483 {
484         iter->name[0] = '\0';
485         iter->nameoff = get_symbol_offset(new_pos);
486         iter->pos = new_pos;
487 }
488 
489 /* Returns false if pos at or past end of file. */
490 static int update_iter(struct kallsym_iter *iter, loff_t pos)
491 {
492         /* Module symbols can be accessed randomly. */
493         if (pos >= kallsyms_num_syms) {
494                 iter->pos = pos;
495                 return get_ksymbol_mod(iter);
496         }
497 
498         /* If we're not on the desired position, reset to new position. */
499         if (pos != iter->pos)
500                 reset_iter(iter, pos);
501 
502         iter->nameoff += get_ksymbol_core(iter);
503         iter->pos++;
504 
505         return 1;
506 }
507 
508 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
509 {
510         (*pos)++;
511 
512         if (!update_iter(m->private, *pos))
513                 return NULL;
514         return p;
515 }
516 
517 static void *s_start(struct seq_file *m, loff_t *pos)
518 {
519         if (!update_iter(m->private, *pos))
520                 return NULL;
521         return m->private;
522 }
523 
524 static void s_stop(struct seq_file *m, void *p)
525 {
526 }
527 
528 static int s_show(struct seq_file *m, void *p)
529 {
530         struct kallsym_iter *iter = m->private;
531 
532         /* Some debugging symbols have no name.  Ignore them. */
533         if (!iter->name[0])
534                 return 0;
535 
536         if (iter->module_name[0]) {
537                 char type;
538 
539                 /*
540                  * Label it "global" if it is exported,
541                  * "local" if not exported.
542                  */
543                 type = iter->exported ? toupper(iter->type) :
544                                         tolower(iter->type);
545                 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
546                            type, iter->name, iter->module_name);
547         } else
548                 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
549                            iter->type, iter->name);
550         return 0;
551 }
552 
553 static const struct seq_operations kallsyms_op = {
554         .start = s_start,
555         .next = s_next,
556         .stop = s_stop,
557         .show = s_show
558 };
559 
560 static int kallsyms_open(struct inode *inode, struct file *file)
561 {
562         /*
563          * We keep iterator in m->private, since normal case is to
564          * s_start from where we left off, so we avoid doing
565          * using get_symbol_offset for every symbol.
566          */
567         struct kallsym_iter *iter;
568         int ret;
569 
570         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
571         if (!iter)
572                 return -ENOMEM;
573         reset_iter(iter, 0);
574 
575         ret = seq_open(file, &kallsyms_op);
576         if (ret == 0)
577                 ((struct seq_file *)file->private_data)->private = iter;
578         else
579                 kfree(iter);
580         return ret;
581 }
582 
583 #ifdef  CONFIG_KGDB_KDB
584 const char *kdb_walk_kallsyms(loff_t *pos)
585 {
586         static struct kallsym_iter kdb_walk_kallsyms_iter;
587         if (*pos == 0) {
588                 memset(&kdb_walk_kallsyms_iter, 0,
589                        sizeof(kdb_walk_kallsyms_iter));
590                 reset_iter(&kdb_walk_kallsyms_iter, 0);
591         }
592         while (1) {
593                 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
594                         return NULL;
595                 ++*pos;
596                 /* Some debugging symbols have no name.  Ignore them. */
597                 if (kdb_walk_kallsyms_iter.name[0])
598                         return kdb_walk_kallsyms_iter.name;
599         }
600 }
601 #endif  /* CONFIG_KGDB_KDB */
602 
603 static const struct file_operations kallsyms_operations = {
604         .open = kallsyms_open,
605         .read = seq_read,
606         .llseek = seq_lseek,
607         .release = seq_release_private,
608 };
609 
610 static int __init kallsyms_init(void)
611 {
612         proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
613         return 0;
614 }
615 device_initcall(kallsyms_init);
616 

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