1/* Look up a symbol in the loaded objects.
2 Copyright (C) 1995-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <alloca.h>
20#include <libintl.h>
21#include <stdlib.h>
22#include <string.h>
23#include <unistd.h>
24#include <ldsodefs.h>
25#include <dl-hash.h>
26#include <dl-machine.h>
27#include <sysdep-cancel.h>
28#include <libc-lock.h>
29#include <tls.h>
30#include <atomic.h>
31
32#include <assert.h>
33
34/* Return nonzero if check_match should consider SYM to fail to match a
35 symbol reference for some machine-specific reason. */
36#ifndef ELF_MACHINE_SYM_NO_MATCH
37# define ELF_MACHINE_SYM_NO_MATCH(sym) 0
38#endif
39
40#define VERSTAG(tag) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag))
41
42
43struct sym_val
44 {
45 const ElfW(Sym) *s;
46 struct link_map *m;
47 };
48
49
50/* Statistics function. */
51#ifdef SHARED
52# define bump_num_relocations() ++GL(dl_num_relocations)
53#else
54# define bump_num_relocations() ((void) 0)
55#endif
56
57/* Utility function for do_lookup_x. The caller is called with undef_name,
58 ref, version, flags and type_class, and those are passed as the first
59 five arguments. The caller then computes sym, symidx, strtab, and map
60 and passes them as the next four arguments. Lastly the caller passes in
61 versioned_sym and num_versions which are modified by check_match during
62 the checking process. */
63static const ElfW(Sym) *
64check_match (const char *const undef_name,
65 const ElfW(Sym) *const ref,
66 const struct r_found_version *const version,
67 const int flags,
68 const int type_class,
69 const ElfW(Sym) *const sym,
70 const Elf_Symndx symidx,
71 const char *const strtab,
72 const struct link_map *const map,
73 const ElfW(Sym) **const versioned_sym,
74 int *const num_versions)
75{
76 unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
77 assert (ELF_RTYPE_CLASS_PLT == 1);
78 if (__glibc_unlikely ((sym->st_value == 0 /* No value. */
79 && sym->st_shndx != SHN_ABS
80 && stt != STT_TLS)
81 || ELF_MACHINE_SYM_NO_MATCH (sym)
82 || (type_class & (sym->st_shndx == SHN_UNDEF))))
83 return NULL;
84
85 /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC,
86 STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no
87 code/data definitions. */
88#define ALLOWED_STT \
89 ((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \
90 | (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC))
91 if (__glibc_unlikely (((1 << stt) & ALLOWED_STT) == 0))
92 return NULL;
93
94 if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
95 /* Not the symbol we are looking for. */
96 return NULL;
97
98 const ElfW(Half) *verstab = map->l_versyms;
99 if (version != NULL)
100 {
101 if (__glibc_unlikely (verstab == NULL))
102 {
103 /* We need a versioned symbol but haven't found any. If
104 this is the object which is referenced in the verneed
105 entry it is a bug in the library since a symbol must
106 not simply disappear.
107
108 It would also be a bug in the object since it means that
109 the list of required versions is incomplete and so the
110 tests in dl-version.c haven't found a problem.*/
111 assert (version->filename == NULL
112 || ! _dl_name_match_p (version->filename, map));
113
114 /* Otherwise we accept the symbol. */
115 }
116 else
117 {
118 /* We can match the version information or use the
119 default one if it is not hidden. */
120 ElfW(Half) ndx = verstab[symidx] & 0x7fff;
121 if ((map->l_versions[ndx].hash != version->hash
122 || strcmp (map->l_versions[ndx].name, version->name))
123 && (version->hidden || map->l_versions[ndx].hash
124 || (verstab[symidx] & 0x8000)))
125 /* It's not the version we want. */
126 return NULL;
127 }
128 }
129 else
130 {
131 /* No specific version is selected. There are two ways we
132 can got here:
133
134 - a binary which does not include versioning information
135 is loaded
136
137 - dlsym() instead of dlvsym() is used to get a symbol which
138 might exist in more than one form
139
140 If the library does not provide symbol version information
141 there is no problem at all: we simply use the symbol if it
142 is defined.
143
144 These two lookups need to be handled differently if the
145 library defines versions. In the case of the old
146 unversioned application the oldest (default) version
147 should be used. In case of a dlsym() call the latest and
148 public interface should be returned. */
149 if (verstab != NULL)
150 {
151 if ((verstab[symidx] & 0x7fff)
152 >= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3))
153 {
154 /* Don't accept hidden symbols. */
155 if ((verstab[symidx] & 0x8000) == 0
156 && (*num_versions)++ == 0)
157 /* No version so far. */
158 *versioned_sym = sym;
159
160 return NULL;
161 }
162 }
163 }
164
165 /* There cannot be another entry for this symbol so stop here. */
166 return sym;
167}
168
169/* Utility function for do_lookup_unique. Add a symbol to TABLE. */
170static void
171enter_unique_sym (struct unique_sym *table, size_t size,
172 unsigned int hash, const char *name,
173 const ElfW(Sym) *sym, const struct link_map *map)
174{
175 size_t idx = hash % size;
176 size_t hash2 = 1 + hash % (size - 2);
177 while (table[idx].name != NULL)
178 {
179 idx += hash2;
180 if (idx >= size)
181 idx -= size;
182 }
183
184 table[idx].hashval = hash;
185 table[idx].name = name;
186 table[idx].sym = sym;
187 table[idx].map = map;
188}
189
190/* Utility function for do_lookup_x. Lookup an STB_GNU_UNIQUE symbol
191 in the unique symbol table, creating a new entry if necessary.
192 Return the matching symbol in RESULT. */
193static void
194do_lookup_unique (const char *undef_name, uint_fast32_t new_hash,
195 const struct link_map *map, struct sym_val *result,
196 int type_class, const ElfW(Sym) *sym, const char *strtab,
197 const ElfW(Sym) *ref, const struct link_map *undef_map)
198{
199 /* We have to determine whether we already found a symbol with this
200 name before. If not then we have to add it to the search table.
201 If we already found a definition we have to use it. */
202
203 struct unique_sym_table *tab
204 = &GL(dl_ns)[map->l_ns]._ns_unique_sym_table;
205
206 __rtld_lock_lock_recursive (tab->lock);
207
208 struct unique_sym *entries = tab->entries;
209 size_t size = tab->size;
210 if (entries != NULL)
211 {
212 size_t idx = new_hash % size;
213 size_t hash2 = 1 + new_hash % (size - 2);
214 while (1)
215 {
216 if (entries[idx].hashval == new_hash
217 && strcmp (entries[idx].name, undef_name) == 0)
218 {
219 if ((type_class & ELF_RTYPE_CLASS_COPY) != 0)
220 {
221 /* We possibly have to initialize the central
222 copy from the copy addressed through the
223 relocation. */
224 result->s = sym;
225 result->m = (struct link_map *) map;
226 }
227 else
228 {
229 result->s = entries[idx].sym;
230 result->m = (struct link_map *) entries[idx].map;
231 }
232 __rtld_lock_unlock_recursive (tab->lock);
233 return;
234 }
235
236 if (entries[idx].name == NULL)
237 break;
238
239 idx += hash2;
240 if (idx >= size)
241 idx -= size;
242 }
243
244 if (size * 3 <= tab->n_elements * 4)
245 {
246 /* Expand the table. */
247#ifdef RTLD_CHECK_FOREIGN_CALL
248 /* This must not happen during runtime relocations. */
249 assert (!RTLD_CHECK_FOREIGN_CALL);
250#endif
251 size_t newsize = _dl_higher_prime_number (size + 1);
252 struct unique_sym *newentries
253 = calloc (sizeof (struct unique_sym), newsize);
254 if (newentries == NULL)
255 {
256 nomem:
257 __rtld_lock_unlock_recursive (tab->lock);
258 _dl_fatal_printf ("out of memory\n");
259 }
260
261 for (idx = 0; idx < size; ++idx)
262 if (entries[idx].name != NULL)
263 enter_unique_sym (newentries, newsize, entries[idx].hashval,
264 entries[idx].name, entries[idx].sym,
265 entries[idx].map);
266
267 tab->free (entries);
268 tab->size = newsize;
269 size = newsize;
270 entries = tab->entries = newentries;
271 tab->free = free;
272 }
273 }
274 else
275 {
276#ifdef RTLD_CHECK_FOREIGN_CALL
277 /* This must not happen during runtime relocations. */
278 assert (!RTLD_CHECK_FOREIGN_CALL);
279#endif
280
281#ifdef SHARED
282 /* If tab->entries is NULL, but tab->size is not, it means
283 this is the second, conflict finding, lookup for
284 LD_TRACE_PRELINKING in _dl_debug_bindings. Don't
285 allocate anything and don't enter anything into the
286 hash table. */
287 if (__glibc_unlikely (tab->size))
288 {
289 assert (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK);
290 goto success;
291 }
292#endif
293
294#define INITIAL_NUNIQUE_SYM_TABLE 31
295 size = INITIAL_NUNIQUE_SYM_TABLE;
296 entries = calloc (sizeof (struct unique_sym), size);
297 if (entries == NULL)
298 goto nomem;
299
300 tab->entries = entries;
301 tab->size = size;
302 tab->free = free;
303 }
304
305 if ((type_class & ELF_RTYPE_CLASS_COPY) != 0)
306 enter_unique_sym (entries, size, new_hash, strtab + sym->st_name, ref,
307 undef_map);
308 else
309 {
310 enter_unique_sym (entries, size,
311 new_hash, strtab + sym->st_name, sym, map);
312
313 if (map->l_type == lt_loaded)
314 /* Make sure we don't unload this object by
315 setting the appropriate flag. */
316 ((struct link_map *) map)->l_flags_1 |= DF_1_NODELETE;
317 }
318 ++tab->n_elements;
319
320#ifdef SHARED
321 success:
322#endif
323 __rtld_lock_unlock_recursive (tab->lock);
324
325 result->s = sym;
326 result->m = (struct link_map *) map;
327}
328
329/* Inner part of the lookup functions. We return a value > 0 if we
330 found the symbol, the value 0 if nothing is found and < 0 if
331 something bad happened. */
332static int
333__attribute_noinline__
334do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
335 unsigned long int *old_hash, const ElfW(Sym) *ref,
336 struct sym_val *result, struct r_scope_elem *scope, size_t i,
337 const struct r_found_version *const version, int flags,
338 struct link_map *skip, int type_class, struct link_map *undef_map)
339{
340 size_t n = scope->r_nlist;
341 /* Make sure we read the value before proceeding. Otherwise we
342 might use r_list pointing to the initial scope and r_nlist being
343 the value after a resize. That is the only path in dl-open.c not
344 protected by GSCOPE. A read barrier here might be to expensive. */
345 __asm volatile ("" : "+r" (n), "+m" (scope->r_list));
346 struct link_map **list = scope->r_list;
347
348 do
349 {
350 const struct link_map *map = list[i]->l_real;
351
352 /* Here come the extra test needed for `_dl_lookup_symbol_skip'. */
353 if (map == skip)
354 continue;
355
356 /* Don't search the executable when resolving a copy reloc. */
357 if ((type_class & ELF_RTYPE_CLASS_COPY) && map->l_type == lt_executable)
358 continue;
359
360 /* Do not look into objects which are going to be removed. */
361 if (map->l_removed)
362 continue;
363
364 /* Print some debugging info if wanted. */
365 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_SYMBOLS))
366 _dl_debug_printf ("symbol=%s; lookup in file=%s [%lu]\n",
367 undef_name, DSO_FILENAME (map->l_name),
368 map->l_ns);
369
370 /* If the hash table is empty there is nothing to do here. */
371 if (map->l_nbuckets == 0)
372 continue;
373
374 Elf_Symndx symidx;
375 int num_versions = 0;
376 const ElfW(Sym) *versioned_sym = NULL;
377
378 /* The tables for this map. */
379 const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
380 const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
381
382 const ElfW(Sym) *sym;
383 const ElfW(Addr) *bitmask = map->l_gnu_bitmask;
384 if (__glibc_likely (bitmask != NULL))
385 {
386 ElfW(Addr) bitmask_word
387 = bitmask[(new_hash / __ELF_NATIVE_CLASS)
388 & map->l_gnu_bitmask_idxbits];
389
390 unsigned int hashbit1 = new_hash & (__ELF_NATIVE_CLASS - 1);
391 unsigned int hashbit2 = ((new_hash >> map->l_gnu_shift)
392 & (__ELF_NATIVE_CLASS - 1));
393
394 if (__glibc_unlikely ((bitmask_word >> hashbit1)
395 & (bitmask_word >> hashbit2) & 1))
396 {
397 Elf32_Word bucket = map->l_gnu_buckets[new_hash
398 % map->l_nbuckets];
399 if (bucket != 0)
400 {
401 const Elf32_Word *hasharr = &map->l_gnu_chain_zero[bucket];
402
403 do
404 if (((*hasharr ^ new_hash) >> 1) == 0)
405 {
406 symidx = hasharr - map->l_gnu_chain_zero;
407 sym = check_match (undef_name, ref, version, flags,
408 type_class, &symtab[symidx], symidx,
409 strtab, map, &versioned_sym,
410 &num_versions);
411 if (sym != NULL)
412 goto found_it;
413 }
414 while ((*hasharr++ & 1u) == 0);
415 }
416 }
417 /* No symbol found. */
418 symidx = SHN_UNDEF;
419 }
420 else
421 {
422 if (*old_hash == 0xffffffff)
423 *old_hash = _dl_elf_hash (undef_name);
424
425 /* Use the old SysV-style hash table. Search the appropriate
426 hash bucket in this object's symbol table for a definition
427 for the same symbol name. */
428 for (symidx = map->l_buckets[*old_hash % map->l_nbuckets];
429 symidx != STN_UNDEF;
430 symidx = map->l_chain[symidx])
431 {
432 sym = check_match (undef_name, ref, version, flags,
433 type_class, &symtab[symidx], symidx,
434 strtab, map, &versioned_sym,
435 &num_versions);
436 if (sym != NULL)
437 goto found_it;
438 }
439 }
440
441 /* If we have seen exactly one versioned symbol while we are
442 looking for an unversioned symbol and the version is not the
443 default version we still accept this symbol since there are
444 no possible ambiguities. */
445 sym = num_versions == 1 ? versioned_sym : NULL;
446
447 if (sym != NULL)
448 {
449 found_it:
450 /* When UNDEF_MAP is NULL, which indicates we are called from
451 do_lookup_x on relocation against protected data, we skip
452 the data definion in the executable from copy reloc. */
453 if (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
454 && undef_map == NULL
455 && map->l_type == lt_executable
456 && type_class == ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA)
457 {
458 const ElfW(Sym) *s;
459 unsigned int i;
460
461#if ! ELF_MACHINE_NO_RELA
462 if (map->l_info[DT_RELA] != NULL
463 && map->l_info[DT_RELASZ] != NULL
464 && map->l_info[DT_RELASZ]->d_un.d_val != 0)
465 {
466 const ElfW(Rela) *rela
467 = (const ElfW(Rela) *) D_PTR (map, l_info[DT_RELA]);
468 unsigned int rela_count
469 = map->l_info[DT_RELASZ]->d_un.d_val / sizeof (*rela);
470
471 for (i = 0; i < rela_count; i++, rela++)
472 if (elf_machine_type_class (ELFW(R_TYPE) (rela->r_info))
473 == ELF_RTYPE_CLASS_COPY)
474 {
475 s = &symtab[ELFW(R_SYM) (rela->r_info)];
476 if (!strcmp (strtab + s->st_name, undef_name))
477 goto skip;
478 }
479 }
480#endif
481#if ! ELF_MACHINE_NO_REL
482 if (map->l_info[DT_REL] != NULL
483 && map->l_info[DT_RELSZ] != NULL
484 && map->l_info[DT_RELSZ]->d_un.d_val != 0)
485 {
486 const ElfW(Rel) *rel
487 = (const ElfW(Rel) *) D_PTR (map, l_info[DT_REL]);
488 unsigned int rel_count
489 = map->l_info[DT_RELSZ]->d_un.d_val / sizeof (*rel);
490
491 for (i = 0; i < rel_count; i++, rel++)
492 if (elf_machine_type_class (ELFW(R_TYPE) (rel->r_info))
493 == ELF_RTYPE_CLASS_COPY)
494 {
495 s = &symtab[ELFW(R_SYM) (rel->r_info)];
496 if (!strcmp (strtab + s->st_name, undef_name))
497 goto skip;
498 }
499 }
500#endif
501 }
502
503 /* Hidden and internal symbols are local, ignore them. */
504 if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym)))
505 goto skip;
506
507 switch (ELFW(ST_BIND) (sym->st_info))
508 {
509 case STB_WEAK:
510 /* Weak definition. Use this value if we don't find another. */
511 if (__glibc_unlikely (GLRO(dl_dynamic_weak)))
512 {
513 if (! result->s)
514 {
515 result->s = sym;
516 result->m = (struct link_map *) map;
517 }
518 break;
519 }
520 /* FALLTHROUGH */
521 case STB_GLOBAL:
522 /* Global definition. Just what we need. */
523 result->s = sym;
524 result->m = (struct link_map *) map;
525 return 1;
526
527 case STB_GNU_UNIQUE:;
528 do_lookup_unique (undef_name, new_hash, map, result, type_class,
529 sym, strtab, ref, undef_map);
530 return 1;
531
532 default:
533 /* Local symbols are ignored. */
534 break;
535 }
536 }
537
538skip:
539 /* If this current map is the one mentioned in the verneed entry
540 and we have not found a weak entry, it is a bug. */
541 if (symidx == STN_UNDEF && version != NULL && version->filename != NULL
542 && __glibc_unlikely (_dl_name_match_p (version->filename, map)))
543 return -1;
544 }
545 while (++i < n);
546
547 /* We have not found anything until now. */
548 return 0;
549}
550
551
552static uint_fast32_t
553dl_new_hash (const char *s)
554{
555 uint_fast32_t h = 5381;
556 for (unsigned char c = *s; c != '\0'; c = *++s)
557 h = h * 33 + c;
558 return h & 0xffffffff;
559}
560
561
562/* Add extra dependency on MAP to UNDEF_MAP. */
563static int
564add_dependency (struct link_map *undef_map, struct link_map *map, int flags)
565{
566 struct link_map *runp;
567 unsigned int i;
568 int result = 0;
569
570 /* Avoid self-references and references to objects which cannot be
571 unloaded anyway. */
572 if (undef_map == map)
573 return 0;
574
575 /* Avoid references to objects which cannot be unloaded anyway. */
576 assert (map->l_type == lt_loaded);
577 if ((map->l_flags_1 & DF_1_NODELETE) != 0)
578 return 0;
579
580 struct link_map_reldeps *l_reldeps
581 = atomic_forced_read (undef_map->l_reldeps);
582
583 /* Make sure l_reldeps is read before l_initfini. */
584 atomic_read_barrier ();
585
586 /* Determine whether UNDEF_MAP already has a reference to MAP. First
587 look in the normal dependencies. */
588 struct link_map **l_initfini = atomic_forced_read (undef_map->l_initfini);
589 if (l_initfini != NULL)
590 {
591 for (i = 0; l_initfini[i] != NULL; ++i)
592 if (l_initfini[i] == map)
593 return 0;
594 }
595
596 /* No normal dependency. See whether we already had to add it
597 to the special list of dynamic dependencies. */
598 unsigned int l_reldepsact = 0;
599 if (l_reldeps != NULL)
600 {
601 struct link_map **list = &l_reldeps->list[0];
602 l_reldepsact = l_reldeps->act;
603 for (i = 0; i < l_reldepsact; ++i)
604 if (list[i] == map)
605 return 0;
606 }
607
608 /* Save serial number of the target MAP. */
609 unsigned long long serial = map->l_serial;
610
611 /* Make sure nobody can unload the object while we are at it. */
612 if (__glibc_unlikely (flags & DL_LOOKUP_GSCOPE_LOCK))
613 {
614 /* We can't just call __rtld_lock_lock_recursive (GL(dl_load_lock))
615 here, that can result in ABBA deadlock. */
616 THREAD_GSCOPE_RESET_FLAG ();
617 __rtld_lock_lock_recursive (GL(dl_load_lock));
618 /* While MAP value won't change, after THREAD_GSCOPE_RESET_FLAG ()
619 it can e.g. point to unallocated memory. So avoid the optimizer
620 treating the above read from MAP->l_serial as ensurance it
621 can safely dereference it. */
622 map = atomic_forced_read (map);
623
624 /* From this point on it is unsafe to dereference MAP, until it
625 has been found in one of the lists. */
626
627 /* Redo the l_initfini check in case undef_map's l_initfini
628 changed in the mean time. */
629 if (undef_map->l_initfini != l_initfini
630 && undef_map->l_initfini != NULL)
631 {
632 l_initfini = undef_map->l_initfini;
633 for (i = 0; l_initfini[i] != NULL; ++i)
634 if (l_initfini[i] == map)
635 goto out_check;
636 }
637
638 /* Redo the l_reldeps check if undef_map's l_reldeps changed in
639 the mean time. */
640 if (undef_map->l_reldeps != NULL)
641 {
642 if (undef_map->l_reldeps != l_reldeps)
643 {
644 struct link_map **list = &undef_map->l_reldeps->list[0];
645 l_reldepsact = undef_map->l_reldeps->act;
646 for (i = 0; i < l_reldepsact; ++i)
647 if (list[i] == map)
648 goto out_check;
649 }
650 else if (undef_map->l_reldeps->act > l_reldepsact)
651 {
652 struct link_map **list
653 = &undef_map->l_reldeps->list[0];
654 i = l_reldepsact;
655 l_reldepsact = undef_map->l_reldeps->act;
656 for (; i < l_reldepsact; ++i)
657 if (list[i] == map)
658 goto out_check;
659 }
660 }
661 }
662 else
663 __rtld_lock_lock_recursive (GL(dl_load_lock));
664
665 /* The object is not yet in the dependency list. Before we add
666 it make sure just one more time the object we are about to
667 reference is still available. There is a brief period in
668 which the object could have been removed since we found the
669 definition. */
670 runp = GL(dl_ns)[undef_map->l_ns]._ns_loaded;
671 while (runp != NULL && runp != map)
672 runp = runp->l_next;
673
674 if (runp != NULL)
675 {
676 /* The object is still available. */
677
678 /* MAP could have been dlclosed, freed and then some other dlopened
679 library could have the same link_map pointer. */
680 if (map->l_serial != serial)
681 goto out_check;
682
683 /* Redo the NODELETE check, as when dl_load_lock wasn't held
684 yet this could have changed. */
685 if ((map->l_flags_1 & DF_1_NODELETE) != 0)
686 goto out;
687
688 /* If the object with the undefined reference cannot be removed ever
689 just make sure the same is true for the object which contains the
690 definition. */
691 if (undef_map->l_type != lt_loaded
692 || (undef_map->l_flags_1 & DF_1_NODELETE) != 0)
693 {
694 map->l_flags_1 |= DF_1_NODELETE;
695 goto out;
696 }
697
698 /* Add the reference now. */
699 if (__glibc_unlikely (l_reldepsact >= undef_map->l_reldepsmax))
700 {
701 /* Allocate more memory for the dependency list. Since this
702 can never happen during the startup phase we can use
703 `realloc'. */
704 struct link_map_reldeps *newp;
705 unsigned int max
706 = undef_map->l_reldepsmax ? undef_map->l_reldepsmax * 2 : 10;
707
708#ifdef RTLD_PREPARE_FOREIGN_CALL
709 RTLD_PREPARE_FOREIGN_CALL;
710#endif
711
712 newp = malloc (sizeof (*newp) + max * sizeof (struct link_map *));
713 if (newp == NULL)
714 {
715 /* If we didn't manage to allocate memory for the list this is
716 no fatal problem. We simply make sure the referenced object
717 cannot be unloaded. This is semantically the correct
718 behavior. */
719 map->l_flags_1 |= DF_1_NODELETE;
720 goto out;
721 }
722 else
723 {
724 if (l_reldepsact)
725 memcpy (&newp->list[0], &undef_map->l_reldeps->list[0],
726 l_reldepsact * sizeof (struct link_map *));
727 newp->list[l_reldepsact] = map;
728 newp->act = l_reldepsact + 1;
729 atomic_write_barrier ();
730 void *old = undef_map->l_reldeps;
731 undef_map->l_reldeps = newp;
732 undef_map->l_reldepsmax = max;
733 if (old)
734 _dl_scope_free (old);
735 }
736 }
737 else
738 {
739 undef_map->l_reldeps->list[l_reldepsact] = map;
740 atomic_write_barrier ();
741 undef_map->l_reldeps->act = l_reldepsact + 1;
742 }
743
744 /* Display information if we are debugging. */
745 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES))
746 _dl_debug_printf ("\
747\nfile=%s [%lu]; needed by %s [%lu] (relocation dependency)\n\n",
748 DSO_FILENAME (map->l_name),
749 map->l_ns,
750 DSO_FILENAME (undef_map->l_name),
751 undef_map->l_ns);
752 }
753 else
754 /* Whoa, that was bad luck. We have to search again. */
755 result = -1;
756
757 out:
758 /* Release the lock. */
759 __rtld_lock_unlock_recursive (GL(dl_load_lock));
760
761 if (__glibc_unlikely (flags & DL_LOOKUP_GSCOPE_LOCK))
762 THREAD_GSCOPE_SET_FLAG ();
763
764 return result;
765
766 out_check:
767 if (map->l_serial != serial)
768 result = -1;
769 goto out;
770}
771
772static void
773_dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
774 const ElfW(Sym) **ref, struct sym_val *value,
775 const struct r_found_version *version, int type_class,
776 int protected);
777
778
779/* Search loaded objects' symbol tables for a definition of the symbol
780 UNDEF_NAME, perhaps with a requested version for the symbol.
781
782 We must never have calls to the audit functions inside this function
783 or in any function which gets called. If this would happen the audit
784 code might create a thread which can throw off all the scope locking. */
785lookup_t
786_dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
787 const ElfW(Sym) **ref,
788 struct r_scope_elem *symbol_scope[],
789 const struct r_found_version *version,
790 int type_class, int flags, struct link_map *skip_map)
791{
792 const uint_fast32_t new_hash = dl_new_hash (undef_name);
793 unsigned long int old_hash = 0xffffffff;
794 struct sym_val current_value = { NULL, NULL };
795 struct r_scope_elem **scope = symbol_scope;
796
797 bump_num_relocations ();
798
799 /* No other flag than DL_LOOKUP_ADD_DEPENDENCY or DL_LOOKUP_GSCOPE_LOCK
800 is allowed if we look up a versioned symbol. */
801 assert (version == NULL
802 || (flags & ~(DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK))
803 == 0);
804
805 size_t i = 0;
806 if (__glibc_unlikely (skip_map != NULL))
807 /* Search the relevant loaded objects for a definition. */
808 while ((*scope)->r_list[i] != skip_map)
809 ++i;
810
811 /* Search the relevant loaded objects for a definition. */
812 for (size_t start = i; *scope != NULL; start = 0, ++scope)
813 {
814 int res = do_lookup_x (undef_name, new_hash, &old_hash, *ref,
815 &current_value, *scope, start, version, flags,
816 skip_map, type_class, undef_map);
817 if (res > 0)
818 break;
819
820 if (__glibc_unlikely (res < 0) && skip_map == NULL)
821 {
822 /* Oh, oh. The file named in the relocation entry does not
823 contain the needed symbol. This code is never reached
824 for unversioned lookups. */
825 assert (version != NULL);
826 const char *reference_name = undef_map ? undef_map->l_name : "";
827 struct dl_exception exception;
828 /* XXX We cannot translate the message. */
829 _dl_exception_create_format
830 (&exception, DSO_FILENAME (reference_name),
831 "symbol %s version %s not defined in file %s"
832 " with link time reference%s",
833 undef_name, version->name, version->filename,
834 res == -2 ? " (no version symbols)" : "");
835 _dl_signal_cexception (0, &exception, N_("relocation error"));
836 _dl_exception_free (&exception);
837 *ref = NULL;
838 return 0;
839 }
840 }
841
842 if (__glibc_unlikely (current_value.s == NULL))
843 {
844 if ((*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
845 && !(GLRO(dl_debug_mask) & DL_DEBUG_UNUSED))
846 {
847 /* We could find no value for a strong reference. */
848 const char *reference_name = undef_map ? undef_map->l_name : "";
849 const char *versionstr = version ? ", version " : "";
850 const char *versionname = (version && version->name
851 ? version->name : "");
852 struct dl_exception exception;
853 /* XXX We cannot translate the message. */
854 _dl_exception_create_format
855 (&exception, DSO_FILENAME (reference_name),
856 "undefined symbol: %s%s%s",
857 undef_name, versionstr, versionname);
858 _dl_signal_cexception (0, &exception, N_("symbol lookup error"));
859 _dl_exception_free (&exception);
860 }
861 *ref = NULL;
862 return 0;
863 }
864
865 int protected = (*ref
866 && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED);
867 if (__glibc_unlikely (protected != 0))
868 {
869 /* It is very tricky. We need to figure out what value to
870 return for the protected symbol. */
871 if (type_class == ELF_RTYPE_CLASS_PLT)
872 {
873 if (current_value.s != NULL && current_value.m != undef_map)
874 {
875 current_value.s = *ref;
876 current_value.m = undef_map;
877 }
878 }
879 else
880 {
881 struct sym_val protected_value = { NULL, NULL };
882
883 for (scope = symbol_scope; *scope != NULL; i = 0, ++scope)
884 if (do_lookup_x (undef_name, new_hash, &old_hash, *ref,
885 &protected_value, *scope, i, version, flags,
886 skip_map,
887 (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
888 && ELFW(ST_TYPE) ((*ref)->st_info) == STT_OBJECT
889 && type_class == ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA)
890 ? ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
891 : ELF_RTYPE_CLASS_PLT, NULL) != 0)
892 break;
893
894 if (protected_value.s != NULL && protected_value.m != undef_map)
895 {
896 current_value.s = *ref;
897 current_value.m = undef_map;
898 }
899 }
900 }
901
902 /* We have to check whether this would bind UNDEF_MAP to an object
903 in the global scope which was dynamically loaded. In this case
904 we have to prevent the latter from being unloaded unless the
905 UNDEF_MAP object is also unloaded. */
906 if (__glibc_unlikely (current_value.m->l_type == lt_loaded)
907 /* Don't do this for explicit lookups as opposed to implicit
908 runtime lookups. */
909 && (flags & DL_LOOKUP_ADD_DEPENDENCY) != 0
910 /* Add UNDEF_MAP to the dependencies. */
911 && add_dependency (undef_map, current_value.m, flags) < 0)
912 /* Something went wrong. Perhaps the object we tried to reference
913 was just removed. Try finding another definition. */
914 return _dl_lookup_symbol_x (undef_name, undef_map, ref,
915 (flags & DL_LOOKUP_GSCOPE_LOCK)
916 ? undef_map->l_scope : symbol_scope,
917 version, type_class, flags, skip_map);
918
919 /* The object is used. */
920 if (__glibc_unlikely (current_value.m->l_used == 0))
921 current_value.m->l_used = 1;
922
923 if (__glibc_unlikely (GLRO(dl_debug_mask)
924 & (DL_DEBUG_BINDINGS|DL_DEBUG_PRELINK)))
925 _dl_debug_bindings (undef_name, undef_map, ref,
926 &current_value, version, type_class, protected);
927
928 *ref = current_value.s;
929 return LOOKUP_VALUE (current_value.m);
930}
931
932
933/* Cache the location of MAP's hash table. */
934
935void
936_dl_setup_hash (struct link_map *map)
937{
938 Elf_Symndx *hash;
939
940 if (__glibc_likely (map->l_info[ADDRIDX (DT_GNU_HASH)] != NULL))
941 {
942 Elf32_Word *hash32
943 = (void *) D_PTR (map, l_info[ADDRIDX (DT_GNU_HASH)]);
944 map->l_nbuckets = *hash32++;
945 Elf32_Word symbias = *hash32++;
946 Elf32_Word bitmask_nwords = *hash32++;
947 /* Must be a power of two. */
948 assert ((bitmask_nwords & (bitmask_nwords - 1)) == 0);
949 map->l_gnu_bitmask_idxbits = bitmask_nwords - 1;
950 map->l_gnu_shift = *hash32++;
951
952 map->l_gnu_bitmask = (ElfW(Addr) *) hash32;
953 hash32 += __ELF_NATIVE_CLASS / 32 * bitmask_nwords;
954
955 map->l_gnu_buckets = hash32;
956 hash32 += map->l_nbuckets;
957 map->l_gnu_chain_zero = hash32 - symbias;
958 return;
959 }
960
961 if (!map->l_info[DT_HASH])
962 return;
963 hash = (void *) D_PTR (map, l_info[DT_HASH]);
964
965 map->l_nbuckets = *hash++;
966 /* Skip nchain. */
967 hash++;
968 map->l_buckets = hash;
969 hash += map->l_nbuckets;
970 map->l_chain = hash;
971}
972
973
974static void
975_dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
976 const ElfW(Sym) **ref, struct sym_val *value,
977 const struct r_found_version *version, int type_class,
978 int protected)
979{
980 const char *reference_name = undef_map->l_name;
981
982 if (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
983 {
984 _dl_debug_printf ("binding file %s [%lu] to %s [%lu]: %s symbol `%s'",
985 DSO_FILENAME (reference_name),
986 undef_map->l_ns,
987 DSO_FILENAME (value->m->l_name),
988 value->m->l_ns,
989 protected ? "protected" : "normal", undef_name);
990 if (version)
991 _dl_debug_printf_c (" [%s]\n", version->name);
992 else
993 _dl_debug_printf_c ("\n");
994 }
995#ifdef SHARED
996 if (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK)
997 {
998/* ELF_RTYPE_CLASS_XXX must match RTYPE_CLASS_XXX used by prelink with
999 LD_TRACE_PRELINKING. */
1000#define RTYPE_CLASS_VALID 8
1001#define RTYPE_CLASS_PLT (8|1)
1002#define RTYPE_CLASS_COPY (8|2)
1003#define RTYPE_CLASS_TLS (8|4)
1004#if ELF_RTYPE_CLASS_PLT != 0 && ELF_RTYPE_CLASS_PLT != 1
1005# error ELF_RTYPE_CLASS_PLT must be 0 or 1!
1006#endif
1007#if ELF_RTYPE_CLASS_COPY != 0 && ELF_RTYPE_CLASS_COPY != 2
1008# error ELF_RTYPE_CLASS_COPY must be 0 or 2!
1009#endif
1010 int conflict = 0;
1011 struct sym_val val = { NULL, NULL };
1012
1013 if ((GLRO(dl_trace_prelink_map) == NULL
1014 || GLRO(dl_trace_prelink_map) == GL(dl_ns)[LM_ID_BASE]._ns_loaded)
1015 && undef_map != GL(dl_ns)[LM_ID_BASE]._ns_loaded)
1016 {
1017 const uint_fast32_t new_hash = dl_new_hash (undef_name);
1018 unsigned long int old_hash = 0xffffffff;
1019 struct unique_sym *saved_entries
1020 = GL(dl_ns)[LM_ID_BASE]._ns_unique_sym_table.entries;
1021
1022 GL(dl_ns)[LM_ID_BASE]._ns_unique_sym_table.entries = NULL;
1023 do_lookup_x (undef_name, new_hash, &old_hash, *ref, &val,
1024 undef_map->l_local_scope[0], 0, version, 0, NULL,
1025 type_class, undef_map);
1026 if (val.s != value->s || val.m != value->m)
1027 conflict = 1;
1028 else if (__glibc_unlikely (undef_map->l_symbolic_in_local_scope)
1029 && val.s
1030 && __glibc_unlikely (ELFW(ST_BIND) (val.s->st_info)
1031 == STB_GNU_UNIQUE))
1032 {
1033 /* If it is STB_GNU_UNIQUE and undef_map's l_local_scope
1034 contains any DT_SYMBOLIC libraries, unfortunately there
1035 can be conflicts even if the above is equal. As symbol
1036 resolution goes from the last library to the first and
1037 if a STB_GNU_UNIQUE symbol is found in some late DT_SYMBOLIC
1038 library, it would be the one that is looked up. */
1039 struct sym_val val2 = { NULL, NULL };
1040 size_t n;
1041 struct r_scope_elem *scope = undef_map->l_local_scope[0];
1042
1043 for (n = 0; n < scope->r_nlist; n++)
1044 if (scope->r_list[n] == val.m)
1045 break;
1046
1047 for (n++; n < scope->r_nlist; n++)
1048 if (scope->r_list[n]->l_info[DT_SYMBOLIC] != NULL
1049 && do_lookup_x (undef_name, new_hash, &old_hash, *ref,
1050 &val2,
1051 &scope->r_list[n]->l_symbolic_searchlist,
1052 0, version, 0, NULL, type_class,
1053 undef_map) > 0)
1054 {
1055 conflict = 1;
1056 val = val2;
1057 break;
1058 }
1059 }
1060 GL(dl_ns)[LM_ID_BASE]._ns_unique_sym_table.entries = saved_entries;
1061 }
1062
1063 if (value->s)
1064 {
1065 /* Keep only ELF_RTYPE_CLASS_PLT and ELF_RTYPE_CLASS_COPY
1066 bits since since prelink only uses them. */
1067 type_class &= ELF_RTYPE_CLASS_PLT | ELF_RTYPE_CLASS_COPY;
1068 if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
1069 == STT_TLS))
1070 /* Clear the RTYPE_CLASS_VALID bit in RTYPE_CLASS_TLS. */
1071 type_class = RTYPE_CLASS_TLS & ~RTYPE_CLASS_VALID;
1072 else if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
1073 == STT_GNU_IFUNC))
1074 /* Set the RTYPE_CLASS_VALID bit. */
1075 type_class |= RTYPE_CLASS_VALID;
1076 }
1077
1078 if (conflict
1079 || GLRO(dl_trace_prelink_map) == undef_map
1080 || GLRO(dl_trace_prelink_map) == NULL
1081 || type_class >= 4)
1082 {
1083 _dl_printf ("%s 0x%0*Zx 0x%0*Zx -> 0x%0*Zx 0x%0*Zx ",
1084 conflict ? "conflict" : "lookup",
1085 (int) sizeof (ElfW(Addr)) * 2,
1086 (size_t) undef_map->l_map_start,
1087 (int) sizeof (ElfW(Addr)) * 2,
1088 (size_t) (((ElfW(Addr)) *ref) - undef_map->l_map_start),
1089 (int) sizeof (ElfW(Addr)) * 2,
1090 (size_t) (value->s ? value->m->l_map_start : 0),
1091 (int) sizeof (ElfW(Addr)) * 2,
1092 (size_t) (value->s ? value->s->st_value : 0));
1093
1094 if (conflict)
1095 _dl_printf ("x 0x%0*Zx 0x%0*Zx ",
1096 (int) sizeof (ElfW(Addr)) * 2,
1097 (size_t) (val.s ? val.m->l_map_start : 0),
1098 (int) sizeof (ElfW(Addr)) * 2,
1099 (size_t) (val.s ? val.s->st_value : 0));
1100
1101 _dl_printf ("/%x %s\n", type_class, undef_name);
1102 }
1103 }
1104#endif
1105}
1106