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 except when the referencing object itself is being removed.
371
372 The second part covers the situation when an object lazily
373 binds to another object while running its destructor, but the
374 destructor of the other object has already run, so that
375 dlclose has set l_removed. It may not always be obvious how
376 to avoid such a scenario to programmers creating DSOs,
377 particularly if C++ vague linkage is involved and triggers
378 symbol interposition.
379
380 Accepting these to-be-removed objects makes the lazy and
381 BIND_NOW cases more similar. (With BIND_NOW, the symbol is
382 resolved early, before the destructor call, so the issue does
383 not arise.). Behavior matches the constructor scenario: the
384 implementation allows binding to symbols of objects whose
385 constructors have not run. In fact, not doing this would be
386 mostly incompatible with symbol interposition. */
387 if (map->l_removed && !(undef_map != NULL && undef_map->l_removed))
388 continue;
389
390 /* Print some debugging info if wanted. */
391 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_SYMBOLS))
392 _dl_debug_printf ("symbol=%s; lookup in file=%s [%lu]\n",
393 undef_name, DSO_FILENAME (map->l_name),
394 map->l_ns);
395
396 /* If the hash table is empty there is nothing to do here. */
397 if (map->l_nbuckets == 0)
398 continue;
399
400 Elf_Symndx symidx;
401 int num_versions = 0;
402 const ElfW(Sym) *versioned_sym = NULL;
403
404 /* The tables for this map. */
405 const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
406 const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
407
408 const ElfW(Sym) *sym;
409 const ElfW(Addr) *bitmask = map->l_gnu_bitmask;
410 if (__glibc_likely (bitmask != NULL))
411 {
412 ElfW(Addr) bitmask_word
413 = bitmask[(new_hash / __ELF_NATIVE_CLASS)
414 & map->l_gnu_bitmask_idxbits];
415
416 unsigned int hashbit1 = new_hash & (__ELF_NATIVE_CLASS - 1);
417 unsigned int hashbit2 = ((new_hash >> map->l_gnu_shift)
418 & (__ELF_NATIVE_CLASS - 1));
419
420 if (__glibc_unlikely ((bitmask_word >> hashbit1)
421 & (bitmask_word >> hashbit2) & 1))
422 {
423 Elf32_Word bucket = map->l_gnu_buckets[new_hash
424 % map->l_nbuckets];
425 if (bucket != 0)
426 {
427 const Elf32_Word *hasharr = &map->l_gnu_chain_zero[bucket];
428
429 do
430 if (((*hasharr ^ new_hash) >> 1) == 0)
431 {
432 symidx = ELF_MACHINE_HASH_SYMIDX (map, hasharr);
433 sym = check_match (undef_name, ref, version, flags,
434 type_class, &symtab[symidx], symidx,
435 strtab, map, &versioned_sym,
436 &num_versions);
437 if (sym != NULL)
438 goto found_it;
439 }
440 while ((*hasharr++ & 1u) == 0);
441 }
442 }
443 /* No symbol found. */
444 symidx = SHN_UNDEF;
445 }
446 else
447 {
448 if (*old_hash == 0xffffffff)
449 *old_hash = _dl_elf_hash (undef_name);
450
451 /* Use the old SysV-style hash table. Search the appropriate
452 hash bucket in this object's symbol table for a definition
453 for the same symbol name. */
454 for (symidx = map->l_buckets[*old_hash % map->l_nbuckets];
455 symidx != STN_UNDEF;
456 symidx = map->l_chain[symidx])
457 {
458 sym = check_match (undef_name, ref, version, flags,
459 type_class, &symtab[symidx], symidx,
460 strtab, map, &versioned_sym,
461 &num_versions);
462 if (sym != NULL)
463 goto found_it;
464 }
465 }
466
467 /* If we have seen exactly one versioned symbol while we are
468 looking for an unversioned symbol and the version is not the
469 default version we still accept this symbol since there are
470 no possible ambiguities. */
471 sym = num_versions == 1 ? versioned_sym : NULL;
472
473 if (sym != NULL)
474 {
475 found_it:
476 /* Hidden and internal symbols are local, ignore them. */
477 if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym)))
478 goto skip;
479
480 if (ELFW(ST_VISIBILITY) (sym->st_other) == STV_PROTECTED)
481 _dl_check_protected_symbol (undef_name, undef_map, ref, map,
482 type_class);
483
484 switch (ELFW(ST_BIND) (sym->st_info))
485 {
486 case STB_WEAK:
487 /* Weak definition. Use this value if we don't find another. */
488 if (__glibc_unlikely (GLRO(dl_dynamic_weak)))
489 {
490 if (! result->s)
491 {
492 result->s = sym;
493 result->m = (struct link_map *) map;
494 }
495 break;
496 }
497 /* FALLTHROUGH */
498 case STB_GLOBAL:
499 /* Global definition. Just what we need. */
500 result->s = sym;
501 result->m = (struct link_map *) map;
502 return 1;
503
504 case STB_GNU_UNIQUE:;
505 do_lookup_unique (undef_name, new_hash, (struct link_map *) map,
506 result, type_class, sym, strtab, ref,
507 undef_map, flags);
508 return 1;
509
510 default:
511 /* Local symbols are ignored. */
512 break;
513 }
514 }
515
516skip:
517 ;
518 }
519 while (++i < n);
520
521 /* We have not found anything until now. */
522 return 0;
523}
524
525
526/* Add extra dependency on MAP to UNDEF_MAP. */
527static int
528add_dependency (struct link_map *undef_map, struct link_map *map, int flags)
529{
530 struct link_map *runp;
531 unsigned int i;
532 int result = 0;
533
534 /* Avoid self-references and references to objects which cannot be
535 unloaded anyway. */
536 if (undef_map == map)
537 return 0;
538
539 /* Avoid references to objects which cannot be unloaded anyway. We
540 do not need to record dependencies if this object goes away
541 during dlopen failure, either. IFUNC resolvers with relocation
542 dependencies may pick an dependency which can be dlclose'd, but
543 such IFUNC resolvers are undefined anyway. */
544 assert (map->l_type == lt_loaded);
545 if (is_nodelete (map, flags))
546 return 0;
547
548 struct link_map_reldeps *l_reldeps
549 = atomic_forced_read (undef_map->l_reldeps);
550
551 /* Make sure l_reldeps is read before l_initfini. */
552 atomic_read_barrier ();
553
554 /* Determine whether UNDEF_MAP already has a reference to MAP. First
555 look in the normal dependencies. */
556 struct link_map **l_initfini = atomic_forced_read (undef_map->l_initfini);
557 if (l_initfini != NULL)
558 {
559 for (i = 0; l_initfini[i] != NULL; ++i)
560 if (l_initfini[i] == map)
561 return 0;
562 }
563
564 /* No normal dependency. See whether we already had to add it
565 to the special list of dynamic dependencies. */
566 unsigned int l_reldepsact = 0;
567 if (l_reldeps != NULL)
568 {
569 struct link_map **list = &l_reldeps->list[0];
570 l_reldepsact = l_reldeps->act;
571 for (i = 0; i < l_reldepsact; ++i)
572 if (list[i] == map)
573 return 0;
574 }
575
576 /* Save serial number of the target MAP. */
577 unsigned long long serial = map->l_serial;
578
579 /* Make sure nobody can unload the object while we are at it. */
580 if (__glibc_unlikely (flags & DL_LOOKUP_GSCOPE_LOCK))
581 {
582 /* We can't just call __rtld_lock_lock_recursive (GL(dl_load_lock))
583 here, that can result in ABBA deadlock. */
584 THREAD_GSCOPE_RESET_FLAG ();
585 __rtld_lock_lock_recursive (GL(dl_load_lock));
586 /* While MAP value won't change, after THREAD_GSCOPE_RESET_FLAG ()
587 it can e.g. point to unallocated memory. So avoid the optimizer
588 treating the above read from MAP->l_serial as ensurance it
589 can safely dereference it. */
590 map = atomic_forced_read (map);
591
592 /* From this point on it is unsafe to dereference MAP, until it
593 has been found in one of the lists. */
594
595 /* Redo the l_initfini check in case undef_map's l_initfini
596 changed in the mean time. */
597 if (undef_map->l_initfini != l_initfini
598 && undef_map->l_initfini != NULL)
599 {
600 l_initfini = undef_map->l_initfini;
601 for (i = 0; l_initfini[i] != NULL; ++i)
602 if (l_initfini[i] == map)
603 goto out_check;
604 }
605
606 /* Redo the l_reldeps check if undef_map's l_reldeps changed in
607 the mean time. */
608 if (undef_map->l_reldeps != NULL)
609 {
610 if (undef_map->l_reldeps != l_reldeps)
611 {
612 struct link_map **list = &undef_map->l_reldeps->list[0];
613 l_reldepsact = undef_map->l_reldeps->act;
614 for (i = 0; i < l_reldepsact; ++i)
615 if (list[i] == map)
616 goto out_check;
617 }
618 else if (undef_map->l_reldeps->act > l_reldepsact)
619 {
620 struct link_map **list
621 = &undef_map->l_reldeps->list[0];
622 i = l_reldepsact;
623 l_reldepsact = undef_map->l_reldeps->act;
624 for (; i < l_reldepsact; ++i)
625 if (list[i] == map)
626 goto out_check;
627 }
628 }
629 }
630 else
631 __rtld_lock_lock_recursive (GL(dl_load_lock));
632
633 /* The object is not yet in the dependency list. Before we add
634 it make sure just one more time the object we are about to
635 reference is still available. There is a brief period in
636 which the object could have been removed since we found the
637 definition. */
638 runp = GL(dl_ns)[undef_map->l_ns]._ns_loaded;
639 while (runp != NULL && runp != map)
640 runp = runp->l_next;
641
642 if (runp != NULL)
643 {
644 /* The object is still available. */
645
646 /* MAP could have been dlclosed, freed and then some other dlopened
647 library could have the same link_map pointer. */
648 if (map->l_serial != serial)
649 goto out_check;
650
651 /* Redo the NODELETE check, as when dl_load_lock wasn't held
652 yet this could have changed. */
653 if (is_nodelete (map, flags))
654 goto out;
655
656 /* If the object with the undefined reference cannot be removed ever
657 just make sure the same is true for the object which contains the
658 definition. */
659 if (undef_map->l_type != lt_loaded || is_nodelete (map, flags))
660 {
661 if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
662 && !is_nodelete (map, flags))
663 {
664 if (undef_map->l_name[0] == '\0')
665 _dl_debug_printf ("\
666marking %s [%lu] as NODELETE due to reference from main program\n",
667 map->l_name, map->l_ns);
668 else
669 _dl_debug_printf ("\
670marking %s [%lu] as NODELETE due to reference from %s [%lu]\n",
671 map->l_name, map->l_ns,
672 undef_map->l_name, undef_map->l_ns);
673 }
674 mark_nodelete (map, flags);
675 goto out;
676 }
677
678 /* Add the reference now. */
679 if (__glibc_unlikely (l_reldepsact >= undef_map->l_reldepsmax))
680 {
681 /* Allocate more memory for the dependency list. Since this
682 can never happen during the startup phase we can use
683 `realloc'. */
684 struct link_map_reldeps *newp;
685 unsigned int max
686 = undef_map->l_reldepsmax ? undef_map->l_reldepsmax * 2 : 10;
687
688#ifdef RTLD_PREPARE_FOREIGN_CALL
689 RTLD_PREPARE_FOREIGN_CALL;
690#endif
691
692 newp = malloc (sizeof (*newp) + max * sizeof (struct link_map *));
693 if (newp == NULL)
694 {
695 /* If we didn't manage to allocate memory for the list this is
696 no fatal problem. We simply make sure the referenced object
697 cannot be unloaded. This is semantically the correct
698 behavior. */
699 if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
700 && !is_nodelete (map, flags))
701 _dl_debug_printf ("\
702marking %s [%lu] as NODELETE due to memory allocation failure\n",
703 map->l_name, map->l_ns);
704 /* In case of non-lazy binding, we could actually report
705 the memory allocation error, but for now, we use the
706 conservative approximation as well. */
707 mark_nodelete (map, flags);
708 goto out;
709 }
710 else
711 {
712 if (l_reldepsact)
713 memcpy (&newp->list[0], &undef_map->l_reldeps->list[0],
714 l_reldepsact * sizeof (struct link_map *));
715 newp->list[l_reldepsact] = map;
716 newp->act = l_reldepsact + 1;
717 atomic_write_barrier ();
718 void *old = undef_map->l_reldeps;
719 undef_map->l_reldeps = newp;
720 undef_map->l_reldepsmax = max;
721 if (old)
722 _dl_scope_free (old);
723 }
724 }
725 else
726 {
727 undef_map->l_reldeps->list[l_reldepsact] = map;
728 atomic_write_barrier ();
729 undef_map->l_reldeps->act = l_reldepsact + 1;
730 }
731
732 /* Display information if we are debugging. */
733 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES))
734 _dl_debug_printf ("\
735\nfile=%s [%lu]; needed by %s [%lu] (relocation dependency)\n\n",
736 DSO_FILENAME (map->l_name),
737 map->l_ns,
738 DSO_FILENAME (undef_map->l_name),
739 undef_map->l_ns);
740 }
741 else
742 /* Whoa, that was bad luck. We have to search again. */
743 result = -1;
744
745 out:
746 /* Release the lock. */
747 __rtld_lock_unlock_recursive (GL(dl_load_lock));
748
749 if (__glibc_unlikely (flags & DL_LOOKUP_GSCOPE_LOCK))
750 THREAD_GSCOPE_SET_FLAG ();
751
752 return result;
753
754 out_check:
755 if (map->l_serial != serial)
756 result = -1;
757 goto out;
758}
759
760
761/* Search loaded objects' symbol tables for a definition of the symbol
762 UNDEF_NAME, perhaps with a requested version for the symbol.
763
764 We must never have calls to the audit functions inside this function
765 or in any function which gets called. If this would happen the audit
766 code might create a thread which can throw off all the scope locking. */
767lookup_t
768_dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
769 const ElfW(Sym) **ref,
770 struct r_scope_elem *symbol_scope[],
771 const struct r_found_version *version,
772 int type_class, int flags, struct link_map *skip_map)
773{
774 const unsigned int new_hash = _dl_new_hash (undef_name);
775 unsigned long int old_hash = 0xffffffff;
776 struct sym_val current_value = { NULL, NULL };
777 struct r_scope_elem **scope = symbol_scope;
778
779 bump_num_relocations ();
780
781 /* DL_LOOKUP_RETURN_NEWEST does not make sense for versioned
782 lookups. */
783 assert (version == NULL || !(flags & DL_LOOKUP_RETURN_NEWEST));
784
785 size_t i = 0;
786 if (__glibc_unlikely (skip_map != NULL))
787 /* Search the relevant loaded objects for a definition. */
788 while ((*scope)->r_list[i] != skip_map)
789 ++i;
790
791 /* Search the relevant loaded objects for a definition. */
792 for (size_t start = i; *scope != NULL; start = 0, ++scope)
793 if (do_lookup_x (undef_name, new_hash, &old_hash, *ref,
794 &current_value, *scope, start, version, flags,
795 skip_map, type_class, undef_map) != 0)
796 break;
797
798 if (__glibc_unlikely (current_value.s == NULL))
799 {
800 if ((*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
801 && !(GLRO(dl_debug_mask) & DL_DEBUG_UNUSED))
802 {
803 /* We could find no value for a strong reference. */
804 const char *reference_name = undef_map ? undef_map->l_name : "";
805 const char *versionstr = version ? ", version " : "";
806 const char *versionname = (version && version->name
807 ? version->name : "");
808 struct dl_exception exception;
809 /* XXX We cannot translate the message. */
810 _dl_exception_create_format
811 (&exception, DSO_FILENAME (reference_name),
812 "undefined symbol: %s%s%s",
813 undef_name, versionstr, versionname);
814 _dl_signal_cexception (0, &exception, N_("symbol lookup error"));
815 _dl_exception_free (&exception);
816 }
817 *ref = NULL;
818 return 0;
819 }
820
821 int protected = (*ref
822 && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED);
823 if (__glibc_unlikely (protected != 0))
824 {
825 /* It is very tricky. We need to figure out what value to
826 return for the protected symbol. */
827 if (type_class == ELF_RTYPE_CLASS_PLT)
828 {
829 if (current_value.s != NULL && current_value.m != undef_map)
830 {
831 current_value.s = *ref;
832 current_value.m = undef_map;
833 }
834 }
835 else
836 {
837 struct sym_val protected_value = { NULL, NULL };
838
839 for (scope = symbol_scope; *scope != NULL; i = 0, ++scope)
840 if (do_lookup_x (undef_name, new_hash, &old_hash, *ref,
841 &protected_value, *scope, i, version, flags,
842 skip_map, ELF_RTYPE_CLASS_PLT, NULL) != 0)
843 break;
844
845 if (protected_value.s != NULL && protected_value.m != undef_map)
846 {
847 current_value.s = *ref;
848 current_value.m = undef_map;
849 }
850 }
851 }
852
853 /* We have to check whether this would bind UNDEF_MAP to an object
854 in the global scope which was dynamically loaded. In this case
855 we have to prevent the latter from being unloaded unless the
856 UNDEF_MAP object is also unloaded. */
857 if (__glibc_unlikely (current_value.m->l_type == lt_loaded)
858 /* Don't do this for explicit lookups as opposed to implicit
859 runtime lookups. */
860 && (flags & DL_LOOKUP_ADD_DEPENDENCY) != 0
861 /* Add UNDEF_MAP to the dependencies. */
862 && add_dependency (undef_map, current_value.m, flags) < 0)
863 /* Something went wrong. Perhaps the object we tried to reference
864 was just removed. Try finding another definition. */
865 return _dl_lookup_symbol_x (undef_name, undef_map, ref,
866 (flags & DL_LOOKUP_GSCOPE_LOCK)
867 ? undef_map->l_scope : symbol_scope,
868 version, type_class, flags, skip_map);
869
870 /* The object is used. */
871 if (__glibc_unlikely (current_value.m->l_used == 0))
872 current_value.m->l_used = 1;
873
874 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS))
875 {
876 const char *reference_name = undef_map->l_name;
877
878 _dl_debug_printf ("binding file %s [%lu] to %s [%lu]: %s symbol `%s'",
879 DSO_FILENAME (reference_name),
880 undef_map->l_ns,
881 DSO_FILENAME (current_value.m->l_name),
882 current_value.m->l_ns,
883 protected ? "protected" : "normal", undef_name);
884 if (version)
885 _dl_debug_printf_c (" [%s]\n", version->name);
886 else
887 _dl_debug_printf_c ("\n");
888 }
889
890
891 *ref = current_value.s;
892 return LOOKUP_VALUE (current_value.m);
893}
894