1/* Look up a symbol in the loaded objects.
2 Copyright (C) 1995-2023 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 <https://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 <dl-new-hash.h>
28#include <dl-protected.h>
29#include <sysdep-cancel.h>
30#include <libc-lock.h>
31#include <tls.h>
32#include <atomic.h>
33#include <elf_machine_sym_no_match.h>
34
35#include <assert.h>
36
37#define VERSTAG(tag) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag))
38
39struct sym_val
40 {
41 const ElfW(Sym) *s;
42 struct link_map *m;
43 };
44
45
46/* Statistics function. */
47#ifdef SHARED
48# define bump_num_relocations() ++GL(dl_num_relocations)
49#else
50# define bump_num_relocations() ((void) 0)
51#endif
52
53/* Utility function for do_lookup_x. The caller is called with undef_name,
54 ref, version, flags and type_class, and those are passed as the first
55 five arguments. The caller then computes sym, symidx, strtab, and map
56 and passes them as the next four arguments. Lastly the caller passes in
57 versioned_sym and num_versions which are modified by check_match during
58 the checking process. */
59static const ElfW(Sym) *
60check_match (const char *const undef_name,
61 const ElfW(Sym) *const ref,
62 const struct r_found_version *const version,
63 const int flags,
64 const int type_class,
65 const ElfW(Sym) *const sym,
66 const Elf_Symndx symidx,
67 const char *const strtab,
68 const struct link_map *const map,
69 const ElfW(Sym) **const versioned_sym,
70 int *const num_versions)
71{
72 unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
73 assert (ELF_RTYPE_CLASS_PLT == 1);
74 if (__glibc_unlikely ((sym->st_value == 0 /* No value. */
75 && sym->st_shndx != SHN_ABS
76 && stt != STT_TLS)
77 || elf_machine_sym_no_match (sym)
78 || (type_class & (sym->st_shndx == SHN_UNDEF))))
79 return NULL;
80
81 /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC,
82 STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no
83 code/data definitions. */
84#define ALLOWED_STT \
85 ((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \
86 | (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC))
87 if (__glibc_unlikely (((1 << stt) & ALLOWED_STT) == 0))
88 return NULL;
89
90 if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
91 /* Not the symbol we are looking for. */
92 return NULL;
93
94 const ElfW(Half) *verstab = map->l_versyms;
95 if (version != NULL)
96 {
97 if (__glibc_unlikely (verstab == NULL))
98 {
99 /* We need a versioned symbol but haven't found any. If
100 this is the object which is referenced in the verneed
101 entry it is a bug in the library since a symbol must
102 not simply disappear.
103
104 It would also be a bug in the object since it means that
105 the list of required versions is incomplete and so the
106 tests in dl-version.c haven't found a problem.*/
107 assert (version->filename == NULL
108 || ! _dl_name_match_p (version->filename, map));
109
110 /* Otherwise we accept the symbol. */
111 }
112 else
113 {
114 /* We can match the version information or use the
115 default one if it is not hidden. */
116 ElfW(Half) ndx = verstab[symidx] & 0x7fff;
117 if ((map->l_versions[ndx].hash != version->hash
118 || strcmp (map->l_versions[ndx].name, version->name))
119 && (version->hidden || map->l_versions[ndx].hash
120 || (verstab[symidx] & 0x8000)))
121 /* It's not the version we want. */
122 return NULL;
123 }
124 }
125 else
126 {
127 /* No specific version is selected. There are two ways we
128 can got here:
129
130 - a binary which does not include versioning information
131 is loaded
132
133 - dlsym() instead of dlvsym() is used to get a symbol which
134 might exist in more than one form
135
136 If the library does not provide symbol version information
137 there is no problem at all: we simply use the symbol if it
138 is defined.
139
140 These two lookups need to be handled differently if the
141 library defines versions. In the case of the old
142 unversioned application the oldest (default) version
143 should be used. In case of a dlsym() call the latest and
144 public interface should be returned. */
145 if (verstab != NULL)
146 {
147 if ((verstab[symidx] & 0x7fff)
148 >= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3))
149 {
150 /* Don't accept hidden symbols. */
151 if ((verstab[symidx] & 0x8000) == 0
152 && (*num_versions)++ == 0)
153 /* No version so far. */
154 *versioned_sym = sym;
155
156 return NULL;
157 }
158 }
159 }
160
161 /* There cannot be another entry for this symbol so stop here. */
162 return sym;
163}
164
165/* Utility function for do_lookup_unique. Add a symbol to TABLE. */
166static void
167enter_unique_sym (struct unique_sym *table, size_t size,
168 unsigned int hash, const char *name,
169 const ElfW(Sym) *sym, const struct link_map *map)
170{
171 size_t idx = hash % size;
172 size_t hash2 = 1 + hash % (size - 2);
173 while (table[idx].name != NULL)
174 {
175 idx += hash2;
176 if (idx >= size)
177 idx -= size;
178 }
179
180 table[idx].hashval = hash;
181 table[idx].name = name;
182 table[idx].sym = sym;
183 table[idx].map = map;
184}
185
186/* Mark MAP as NODELETE according to the lookup mode in FLAGS. During
187 initial relocation, NODELETE state is pending only. */
188static void
189mark_nodelete (struct link_map *map, int flags)
190{
191 if (flags & DL_LOOKUP_FOR_RELOCATE)
192 map->l_nodelete_pending = true;
193 else
194 map->l_nodelete_active = true;
195}
196
197/* Return true if MAP is marked as NODELETE according to the lookup
198 mode in FLAGS> */
199static bool
200is_nodelete (struct link_map *map, int flags)
201{
202 /* Non-pending NODELETE always counts. Pending NODELETE only counts
203 during initial relocation processing. */
204 return map->l_nodelete_active
205 || ((flags & DL_LOOKUP_FOR_RELOCATE) && map->l_nodelete_pending);
206}
207
208/* Utility function for do_lookup_x. Lookup an STB_GNU_UNIQUE symbol
209 in the unique symbol table, creating a new entry if necessary.
210 Return the matching symbol in RESULT. */
211static void
212do_lookup_unique (const char *undef_name, unsigned int new_hash,
213 struct link_map *map, struct sym_val *result,
214 int type_class, const ElfW(Sym) *sym, const char *strtab,
215 const ElfW(Sym) *ref, const struct link_map *undef_map,
216 int flags)
217{
218 /* We have to determine whether we already found a symbol with this
219 name before. If not then we have to add it to the search table.
220 If we already found a definition we have to use it. */
221
222 struct unique_sym_table *tab
223 = &GL(dl_ns)[map->l_ns]._ns_unique_sym_table;
224
225 __rtld_lock_lock_recursive (tab->lock);
226
227 struct unique_sym *entries = tab->entries;
228 size_t size = tab->size;
229 if (entries != NULL)
230 {
231 size_t idx = new_hash % size;
232 size_t hash2 = 1 + new_hash % (size - 2);
233 while (1)
234 {
235 if (entries[idx].hashval == new_hash
236 && strcmp (entries[idx].name, undef_name) == 0)
237 {
238 if ((type_class & ELF_RTYPE_CLASS_COPY) != 0)
239 {
240 /* We possibly have to initialize the central
241 copy from the copy addressed through the
242 relocation. */
243 result->s = sym;
244 result->m = map;
245 }
246 else
247 {
248 result->s = entries[idx].sym;
249 result->m = (struct link_map *) entries[idx].map;
250 }
251 __rtld_lock_unlock_recursive (tab->lock);
252 return;
253 }
254
255 if (entries[idx].name == NULL)
256 break;
257
258 idx += hash2;
259 if (idx >= size)
260 idx -= size;
261 }
262
263 if (size * 3 <= tab->n_elements * 4)
264 {
265 /* Expand the table. */
266#ifdef RTLD_CHECK_FOREIGN_CALL
267 /* This must not happen during runtime relocations. */
268 assert (!RTLD_CHECK_FOREIGN_CALL);
269#endif
270 size_t newsize = _dl_higher_prime_number (size + 1);
271 struct unique_sym *newentries
272 = calloc (sizeof (struct unique_sym), newsize);
273 if (newentries == NULL)
274 {
275 nomem:
276 __rtld_lock_unlock_recursive (tab->lock);
277 _dl_fatal_printf ("out of memory\n");
278 }
279
280 for (idx = 0; idx < size; ++idx)
281 if (entries[idx].name != NULL)
282 enter_unique_sym (newentries, newsize, entries[idx].hashval,
283 entries[idx].name, entries[idx].sym,
284 entries[idx].map);
285
286 tab->free (entries);
287 tab->size = newsize;
288 size = newsize;
289 entries = tab->entries = newentries;
290 tab->free = __rtld_free;
291 }
292 }
293 else
294 {
295#ifdef RTLD_CHECK_FOREIGN_CALL
296 /* This must not happen during runtime relocations. */
297 assert (!RTLD_CHECK_FOREIGN_CALL);
298#endif
299
300#define INITIAL_NUNIQUE_SYM_TABLE 31
301 size = INITIAL_NUNIQUE_SYM_TABLE;
302 entries = calloc (sizeof (struct unique_sym), size);
303 if (entries == NULL)
304 goto nomem;
305
306 tab->entries = entries;
307 tab->size = size;
308 tab->free = __rtld_free;
309 }
310
311 if ((type_class & ELF_RTYPE_CLASS_COPY) != 0)
312 enter_unique_sym (entries, size, new_hash, strtab + sym->st_name, ref,
313 undef_map);
314 else
315 {
316 enter_unique_sym (entries, size,
317 new_hash, strtab + sym->st_name, sym, map);
318
319 if (map->l_type == lt_loaded && !is_nodelete (map, flags))
320 {
321 /* Make sure we don't unload this object by
322 setting the appropriate flag. */
323 if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS))
324 _dl_debug_printf ("\
325marking %s [%lu] as NODELETE due to unique symbol\n",
326 map->l_name, map->l_ns);
327 mark_nodelete (map, flags);
328 }
329 }
330 ++tab->n_elements;
331
332 __rtld_lock_unlock_recursive (tab->lock);
333
334 result->s = sym;
335 result->m = (struct link_map *) map;
336}
337
338/* Inner part of the lookup functions. We return a value > 0 if we
339 found the symbol, the value 0 if nothing is found and < 0 if
340 something bad happened. */
341static int
342__attribute_noinline__
343do_lookup_x (const char *undef_name, unsigned int new_hash,
344 unsigned long int *old_hash, const ElfW(Sym) *ref,
345 struct sym_val *result, struct r_scope_elem *scope, size_t i,
346 const struct r_found_version *const version, int flags,
347 struct link_map *skip, int type_class, struct link_map *undef_map)
348{
349 size_t n = scope->r_nlist;
350 /* Make sure we read the value before proceeding. Otherwise we
351 might use r_list pointing to the initial scope and r_nlist being
352 the value after a resize. That is the only path in dl-open.c not
353 protected by GSCOPE. A read barrier here might be to expensive. */
354 __asm volatile ("" : "+r" (n), "+m" (scope->r_list));
355 struct link_map **list = scope->r_list;
356
357 do
358 {
359 const struct link_map *map = list[i]->l_real;
360
361 /* Here come the extra test needed for `_dl_lookup_symbol_skip'. */
362 if (map == skip)
363 continue;
364
365 /* Don't search the executable when resolving a copy reloc. */
366 if ((type_class & ELF_RTYPE_CLASS_COPY) && map->l_type == lt_executable)
367 continue;
368
369 /* Do not look into objects which are going to be removed. */
370 if (map->l_removed)
371 continue;
372
373 /* Print some debugging info if wanted. */
374 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_SYMBOLS))
375 _dl_debug_printf ("symbol=%s; lookup in file=%s [%lu]\n",
376 undef_name, DSO_FILENAME (map->l_name),
377 map->l_ns);
378
379 /* If the hash table is empty there is nothing to do here. */
380 if (map->l_nbuckets == 0)
381 continue;
382
383 Elf_Symndx symidx;
384 int num_versions = 0;
385 const ElfW(Sym) *versioned_sym = NULL;
386
387 /* The tables for this map. */
388 const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
389 const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
390
391 const ElfW(Sym) *sym;
392 const ElfW(Addr) *bitmask = map->l_gnu_bitmask;
393 if (__glibc_likely (bitmask != NULL))
394 {
395 ElfW(Addr) bitmask_word
396 = bitmask[(new_hash / __ELF_NATIVE_CLASS)
397 & map->l_gnu_bitmask_idxbits];
398
399 unsigned int hashbit1 = new_hash & (__ELF_NATIVE_CLASS - 1);
400 unsigned int hashbit2 = ((new_hash >> map->l_gnu_shift)
401 & (__ELF_NATIVE_CLASS - 1));
402
403 if (__glibc_unlikely ((bitmask_word >> hashbit1)
404 & (bitmask_word >> hashbit2) & 1))
405 {
406 Elf32_Word bucket = map->l_gnu_buckets[new_hash
407 % map->l_nbuckets];
408 if (bucket != 0)
409 {
410 const Elf32_Word *hasharr = &map->l_gnu_chain_zero[bucket];
411
412 do
413 if (((*hasharr ^ new_hash) >> 1) == 0)
414 {
415 symidx = ELF_MACHINE_HASH_SYMIDX (map, hasharr);
416 sym = check_match (undef_name, ref, version, flags,
417 type_class, &symtab[symidx], symidx,
418 strtab, map, &versioned_sym,
419 &num_versions);
420 if (sym != NULL)
421 goto found_it;
422 }
423 while ((*hasharr++ & 1u) == 0);
424 }
425 }
426 /* No symbol found. */
427 symidx = SHN_UNDEF;
428 }
429 else
430 {
431 if (*old_hash == 0xffffffff)
432 *old_hash = _dl_elf_hash (undef_name);
433
434 /* Use the old SysV-style hash table. Search the appropriate
435 hash bucket in this object's symbol table for a definition
436 for the same symbol name. */
437 for (symidx = map->l_buckets[*old_hash % map->l_nbuckets];
438 symidx != STN_UNDEF;
439 symidx = map->l_chain[symidx])
440 {
441 sym = check_match (undef_name, ref, version, flags,
442 type_class, &symtab[symidx], symidx,
443 strtab, map, &versioned_sym,
444 &num_versions);
445 if (sym != NULL)
446 goto found_it;
447 }
448 }
449
450 /* If we have seen exactly one versioned symbol while we are
451 looking for an unversioned symbol and the version is not the
452 default version we still accept this symbol since there are
453 no possible ambiguities. */
454 sym = num_versions == 1 ? versioned_sym : NULL;
455
456 if (sym != NULL)
457 {
458 found_it:
459 /* Hidden and internal symbols are local, ignore them. */
460 if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym)))
461 goto skip;
462
463 if (ELFW(ST_VISIBILITY) (sym->st_other) == STV_PROTECTED)
464 _dl_check_protected_symbol (undef_name, undef_map, ref, map,
465 type_class);
466
467 switch (ELFW(ST_BIND) (sym->st_info))
468 {
469 case STB_WEAK:
470 /* Weak definition. Use this value if we don't find another. */
471 if (__glibc_unlikely (GLRO(dl_dynamic_weak)))
472 {
473 if (! result->s)
474 {
475 result->s = sym;
476 result->m = (struct link_map *) map;
477 }
478 break;
479 }
480 /* FALLTHROUGH */
481 case STB_GLOBAL:
482 /* Global definition. Just what we need. */
483 result->s = sym;
484 result->m = (struct link_map *) map;
485 return 1;
486
487 case STB_GNU_UNIQUE:;
488 do_lookup_unique (undef_name, new_hash, (struct link_map *) map,
489 result, type_class, sym, strtab, ref,
490 undef_map, flags);
491 return 1;
492
493 default:
494 /* Local symbols are ignored. */
495 break;
496 }
497 }
498
499skip:
500 ;
501 }
502 while (++i < n);
503
504 /* We have not found anything until now. */
505 return 0;
506}
507
508
509/* Add extra dependency on MAP to UNDEF_MAP. */
510static int
511add_dependency (struct link_map *undef_map, struct link_map *map, int flags)
512{
513 struct link_map *runp;
514 unsigned int i;
515 int result = 0;
516
517 /* Avoid self-references and references to objects which cannot be
518 unloaded anyway. */
519 if (undef_map == map)
520 return 0;
521
522 /* Avoid references to objects which cannot be unloaded anyway. We
523 do not need to record dependencies if this object goes away
524 during dlopen failure, either. IFUNC resolvers with relocation
525 dependencies may pick an dependency which can be dlclose'd, but
526 such IFUNC resolvers are undefined anyway. */
527 assert (map->l_type == lt_loaded);
528 if (is_nodelete (map, flags))
529 return 0;
530
531 struct link_map_reldeps *l_reldeps
532 = atomic_forced_read (undef_map->l_reldeps);
533
534 /* Make sure l_reldeps is read before l_initfini. */
535 atomic_read_barrier ();
536
537 /* Determine whether UNDEF_MAP already has a reference to MAP. First
538 look in the normal dependencies. */
539 struct link_map **l_initfini = atomic_forced_read (undef_map->l_initfini);
540 if (l_initfini != NULL)
541 {
542 for (i = 0; l_initfini[i] != NULL; ++i)
543 if (l_initfini[i] == map)
544 return 0;
545 }
546
547 /* No normal dependency. See whether we already had to add it
548 to the special list of dynamic dependencies. */
549 unsigned int l_reldepsact = 0;
550 if (l_reldeps != NULL)
551 {
552 struct link_map **list = &l_reldeps->list[0];
553 l_reldepsact = l_reldeps->act;
554 for (i = 0; i < l_reldepsact; ++i)
555 if (list[i] == map)
556 return 0;
557 }
558
559 /* Save serial number of the target MAP. */
560 unsigned long long serial = map->l_serial;
561
562 /* Make sure nobody can unload the object while we are at it. */
563 if (__glibc_unlikely (flags & DL_LOOKUP_GSCOPE_LOCK))
564 {
565 /* We can't just call __rtld_lock_lock_recursive (GL(dl_load_lock))
566 here, that can result in ABBA deadlock. */
567 THREAD_GSCOPE_RESET_FLAG ();
568 __rtld_lock_lock_recursive (GL(dl_load_lock));
569 /* While MAP value won't change, after THREAD_GSCOPE_RESET_FLAG ()
570 it can e.g. point to unallocated memory. So avoid the optimizer
571 treating the above read from MAP->l_serial as ensurance it
572 can safely dereference it. */
573 map = atomic_forced_read (map);
574
575 /* From this point on it is unsafe to dereference MAP, until it
576 has been found in one of the lists. */
577
578 /* Redo the l_initfini check in case undef_map's l_initfini
579 changed in the mean time. */
580 if (undef_map->l_initfini != l_initfini
581 && undef_map->l_initfini != NULL)
582 {
583 l_initfini = undef_map->l_initfini;
584 for (i = 0; l_initfini[i] != NULL; ++i)
585 if (l_initfini[i] == map)
586 goto out_check;
587 }
588
589 /* Redo the l_reldeps check if undef_map's l_reldeps changed in
590 the mean time. */
591 if (undef_map->l_reldeps != NULL)
592 {
593 if (undef_map->l_reldeps != l_reldeps)
594 {
595 struct link_map **list = &undef_map->l_reldeps->list[0];
596 l_reldepsact = undef_map->l_reldeps->act;
597 for (i = 0; i < l_reldepsact; ++i)
598 if (list[i] == map)
599 goto out_check;
600 }
601 else if (undef_map->l_reldeps->act > l_reldepsact)
602 {
603 struct link_map **list
604 = &undef_map->l_reldeps->list[0];
605 i = l_reldepsact;
606 l_reldepsact = undef_map->l_reldeps->act;
607 for (; i < l_reldepsact; ++i)
608 if (list[i] == map)
609 goto out_check;
610 }
611 }
612 }
613 else
614 __rtld_lock_lock_recursive (GL(dl_load_lock));
615
616 /* The object is not yet in the dependency list. Before we add
617 it make sure just one more time the object we are about to
618 reference is still available. There is a brief period in
619 which the object could have been removed since we found the
620 definition. */
621 runp = GL(dl_ns)[undef_map->l_ns]._ns_loaded;
622 while (runp != NULL && runp != map)
623 runp = runp->l_next;
624
625 if (runp != NULL)
626 {
627 /* The object is still available. */
628
629 /* MAP could have been dlclosed, freed and then some other dlopened
630 library could have the same link_map pointer. */
631 if (map->l_serial != serial)
632 goto out_check;
633
634 /* Redo the NODELETE check, as when dl_load_lock wasn't held
635 yet this could have changed. */
636 if (is_nodelete (map, flags))
637 goto out;
638
639 /* If the object with the undefined reference cannot be removed ever
640 just make sure the same is true for the object which contains the
641 definition. */
642 if (undef_map->l_type != lt_loaded || is_nodelete (map, flags))
643 {
644 if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
645 && !is_nodelete (map, flags))
646 {
647 if (undef_map->l_name[0] == '\0')
648 _dl_debug_printf ("\
649marking %s [%lu] as NODELETE due to reference from main program\n",
650 map->l_name, map->l_ns);
651 else
652 _dl_debug_printf ("\
653marking %s [%lu] as NODELETE due to reference from %s [%lu]\n",
654 map->l_name, map->l_ns,
655 undef_map->l_name, undef_map->l_ns);
656 }
657 mark_nodelete (map, flags);
658 goto out;
659 }
660
661 /* Add the reference now. */
662 if (__glibc_unlikely (l_reldepsact >= undef_map->l_reldepsmax))
663 {
664 /* Allocate more memory for the dependency list. Since this
665 can never happen during the startup phase we can use
666 `realloc'. */
667 struct link_map_reldeps *newp;
668 unsigned int max
669 = undef_map->l_reldepsmax ? undef_map->l_reldepsmax * 2 : 10;
670
671#ifdef RTLD_PREPARE_FOREIGN_CALL
672 RTLD_PREPARE_FOREIGN_CALL;
673#endif
674
675 newp = malloc (sizeof (*newp) + max * sizeof (struct link_map *));
676 if (newp == NULL)
677 {
678 /* If we didn't manage to allocate memory for the list this is
679 no fatal problem. We simply make sure the referenced object
680 cannot be unloaded. This is semantically the correct
681 behavior. */
682 if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
683 && !is_nodelete (map, flags))
684 _dl_debug_printf ("\
685marking %s [%lu] as NODELETE due to memory allocation failure\n",
686 map->l_name, map->l_ns);
687 /* In case of non-lazy binding, we could actually report
688 the memory allocation error, but for now, we use the
689 conservative approximation as well. */
690 mark_nodelete (map, flags);
691 goto out;
692 }
693 else
694 {
695 if (l_reldepsact)
696 memcpy (&newp->list[0], &undef_map->l_reldeps->list[0],
697 l_reldepsact * sizeof (struct link_map *));
698 newp->list[l_reldepsact] = map;
699 newp->act = l_reldepsact + 1;
700 atomic_write_barrier ();
701 void *old = undef_map->l_reldeps;
702 undef_map->l_reldeps = newp;
703 undef_map->l_reldepsmax = max;
704 if (old)
705 _dl_scope_free (old);
706 }
707 }
708 else
709 {
710 undef_map->l_reldeps->list[l_reldepsact] = map;
711 atomic_write_barrier ();
712 undef_map->l_reldeps->act = l_reldepsact + 1;
713 }
714
715 /* Display information if we are debugging. */
716 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES))
717 _dl_debug_printf ("\
718\nfile=%s [%lu]; needed by %s [%lu] (relocation dependency)\n\n",
719 DSO_FILENAME (map->l_name),
720 map->l_ns,
721 DSO_FILENAME (undef_map->l_name),
722 undef_map->l_ns);
723 }
724 else
725 /* Whoa, that was bad luck. We have to search again. */
726 result = -1;
727
728 out:
729 /* Release the lock. */
730 __rtld_lock_unlock_recursive (GL(dl_load_lock));
731
732 if (__glibc_unlikely (flags & DL_LOOKUP_GSCOPE_LOCK))
733 THREAD_GSCOPE_SET_FLAG ();
734
735 return result;
736
737 out_check:
738 if (map->l_serial != serial)
739 result = -1;
740 goto out;
741}
742
743
744/* Search loaded objects' symbol tables for a definition of the symbol
745 UNDEF_NAME, perhaps with a requested version for the symbol.
746
747 We must never have calls to the audit functions inside this function
748 or in any function which gets called. If this would happen the audit
749 code might create a thread which can throw off all the scope locking. */
750lookup_t
751_dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
752 const ElfW(Sym) **ref,
753 struct r_scope_elem *symbol_scope[],
754 const struct r_found_version *version,
755 int type_class, int flags, struct link_map *skip_map)
756{
757 const unsigned int new_hash = _dl_new_hash (undef_name);
758 unsigned long int old_hash = 0xffffffff;
759 struct sym_val current_value = { NULL, NULL };
760 struct r_scope_elem **scope = symbol_scope;
761
762 bump_num_relocations ();
763
764 /* DL_LOOKUP_RETURN_NEWEST does not make sense for versioned
765 lookups. */
766 assert (version == NULL || !(flags & DL_LOOKUP_RETURN_NEWEST));
767
768 size_t i = 0;
769 if (__glibc_unlikely (skip_map != NULL))
770 /* Search the relevant loaded objects for a definition. */
771 while ((*scope)->r_list[i] != skip_map)
772 ++i;
773
774 /* Search the relevant loaded objects for a definition. */
775 for (size_t start = i; *scope != NULL; start = 0, ++scope)
776 if (do_lookup_x (undef_name, new_hash, &old_hash, *ref,
777 &current_value, *scope, start, version, flags,
778 skip_map, type_class, undef_map) != 0)
779 break;
780
781 if (__glibc_unlikely (current_value.s == NULL))
782 {
783 if ((*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
784 && !(GLRO(dl_debug_mask) & DL_DEBUG_UNUSED))
785 {
786 /* We could find no value for a strong reference. */
787 const char *reference_name = undef_map ? undef_map->l_name : "";
788 const char *versionstr = version ? ", version " : "";
789 const char *versionname = (version && version->name
790 ? version->name : "");
791 struct dl_exception exception;
792 /* XXX We cannot translate the message. */
793 _dl_exception_create_format
794 (&exception, DSO_FILENAME (reference_name),
795 "undefined symbol: %s%s%s",
796 undef_name, versionstr, versionname);
797 _dl_signal_cexception (0, &exception, N_("symbol lookup error"));
798 _dl_exception_free (&exception);
799 }
800 *ref = NULL;
801 return 0;
802 }
803
804 int protected = (*ref
805 && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED);
806 if (__glibc_unlikely (protected != 0))
807 {
808 /* It is very tricky. We need to figure out what value to
809 return for the protected symbol. */
810 if (type_class == ELF_RTYPE_CLASS_PLT)
811 {
812 if (current_value.s != NULL && current_value.m != undef_map)
813 {
814 current_value.s = *ref;
815 current_value.m = undef_map;
816 }
817 }
818 else
819 {
820 struct sym_val protected_value = { NULL, NULL };
821
822 for (scope = symbol_scope; *scope != NULL; i = 0, ++scope)
823 if (do_lookup_x (undef_name, new_hash, &old_hash, *ref,
824 &protected_value, *scope, i, version, flags,
825 skip_map, ELF_RTYPE_CLASS_PLT, NULL) != 0)
826 break;
827
828 if (protected_value.s != NULL && protected_value.m != undef_map)
829 {
830 current_value.s = *ref;
831 current_value.m = undef_map;
832 }
833 }
834 }
835
836 /* We have to check whether this would bind UNDEF_MAP to an object
837 in the global scope which was dynamically loaded. In this case
838 we have to prevent the latter from being unloaded unless the
839 UNDEF_MAP object is also unloaded. */
840 if (__glibc_unlikely (current_value.m->l_type == lt_loaded)
841 /* Don't do this for explicit lookups as opposed to implicit
842 runtime lookups. */
843 && (flags & DL_LOOKUP_ADD_DEPENDENCY) != 0
844 /* Add UNDEF_MAP to the dependencies. */
845 && add_dependency (undef_map, current_value.m, flags) < 0)
846 /* Something went wrong. Perhaps the object we tried to reference
847 was just removed. Try finding another definition. */
848 return _dl_lookup_symbol_x (undef_name, undef_map, ref,
849 (flags & DL_LOOKUP_GSCOPE_LOCK)
850 ? undef_map->l_scope : symbol_scope,
851 version, type_class, flags, skip_map);
852
853 /* The object is used. */
854 if (__glibc_unlikely (current_value.m->l_used == 0))
855 current_value.m->l_used = 1;
856
857 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS))
858 {
859 const char *reference_name = undef_map->l_name;
860
861 _dl_debug_printf ("binding file %s [%lu] to %s [%lu]: %s symbol `%s'",
862 DSO_FILENAME (reference_name),
863 undef_map->l_ns,
864 DSO_FILENAME (current_value.m->l_name),
865 current_value.m->l_ns,
866 protected ? "protected" : "normal", undef_name);
867 if (version)
868 _dl_debug_printf_c (" [%s]\n", version->name);
869 else
870 _dl_debug_printf_c ("\n");
871 }
872
873
874 *ref = current_value.s;
875 return LOOKUP_VALUE (current_value.m);
876}
877