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.
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.
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.
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/>. */
26 #include <dl-machine.h>
27 #include <sysdep-cancel.h>
28 #include <libc-lock.h>
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
40 #define VERSTAG(tag) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag))
50 /* Statistics function. */
52 # define bump_num_relocations() ++GL(dl_num_relocations)
54 # define bump_num_relocations() ((void) 0)
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. */
63 static const ElfW(Sym
) *
64 check_match (const char *const undef_name
,
65 const ElfW(Sym
) *const ref
,
66 const struct r_found_version
*const version
,
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
)
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
81 || ELF_MACHINE_SYM_NO_MATCH (sym
)
82 || (type_class
& (sym
->st_shndx
== SHN_UNDEF
))))
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. */
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))
94 if (sym
!= ref
&& strcmp (strtab
+ sym
->st_name
, undef_name
))
95 /* Not the symbol we are looking for. */
98 const ElfW(Half
) *verstab
= map
->l_versyms
;
101 if (__glibc_unlikely (verstab
== NULL
))
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.
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
));
114 /* Otherwise we accept the symbol. */
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. */
131 /* No specific version is selected. There are two ways we
134 - a binary which does not include versioning information
137 - dlsym() instead of dlvsym() is used to get a symbol which
138 might exist in more than one form
140 If the library does not provide symbol version information
141 there is no problem at all: we simply use the symbol if it
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. */
151 if ((verstab
[symidx
] & 0x7fff)
152 >= ((flags
& DL_LOOKUP_RETURN_NEWEST
) ? 2 : 3))
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
;
165 /* There cannot be another entry for this symbol so stop here. */
169 /* Utility function for do_lookup_unique. Add a symbol to TABLE. */
171 enter_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
)
175 size_t idx
= hash
% size
;
176 size_t hash2
= 1 + hash
% (size
- 2);
177 while (table
[idx
].name
!= NULL
)
184 table
[idx
].hashval
= hash
;
185 table
[idx
].name
= name
;
186 table
[idx
].sym
= sym
;
187 table
[idx
].map
= map
;
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. */
194 do_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
)
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. */
203 struct unique_sym_table
*tab
204 = &GL(dl_ns
)[map
->l_ns
]._ns_unique_sym_table
;
206 __rtld_lock_lock_recursive (tab
->lock
);
208 struct unique_sym
*entries
= tab
->entries
;
209 size_t size
= tab
->size
;
212 size_t idx
= new_hash
% size
;
213 size_t hash2
= 1 + new_hash
% (size
- 2);
216 if (entries
[idx
].hashval
== new_hash
217 && strcmp (entries
[idx
].name
, undef_name
) == 0)
219 if ((type_class
& ELF_RTYPE_CLASS_COPY
) != 0)
221 /* We possibly have to initialize the central
222 copy from the copy addressed through the
225 result
->m
= (struct link_map
*) map
;
229 result
->s
= entries
[idx
].sym
;
230 result
->m
= (struct link_map
*) entries
[idx
].map
;
232 __rtld_lock_unlock_recursive (tab
->lock
);
236 if (entries
[idx
].name
== NULL
)
244 if (size
* 3 <= tab
->n_elements
* 4)
246 /* Expand the table. */
247 #ifdef RTLD_CHECK_FOREIGN_CALL
248 /* This must not happen during runtime relocations. */
249 assert (!RTLD_CHECK_FOREIGN_CALL
);
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
)
257 __rtld_lock_unlock_recursive (tab
->lock
);
258 _dl_fatal_printf ("out of memory\n");
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
,
270 entries
= tab
->entries
= newentries
;
276 #ifdef RTLD_CHECK_FOREIGN_CALL
277 /* This must not happen during runtime relocations. */
278 assert (!RTLD_CHECK_FOREIGN_CALL
);
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
287 if (__glibc_unlikely (tab
->size
))
289 assert (GLRO(dl_debug_mask
) & DL_DEBUG_PRELINK
);
294 #define INITIAL_NUNIQUE_SYM_TABLE 31
295 size
= INITIAL_NUNIQUE_SYM_TABLE
;
296 entries
= calloc (sizeof (struct unique_sym
), size
);
300 tab
->entries
= entries
;
305 if ((type_class
& ELF_RTYPE_CLASS_COPY
) != 0)
306 enter_unique_sym (entries
, size
, new_hash
, strtab
+ sym
->st_name
, ref
,
310 enter_unique_sym (entries
, size
,
311 new_hash
, strtab
+ sym
->st_name
, sym
, map
);
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
;
323 __rtld_lock_unlock_recursive (tab
->lock
);
326 result
->m
= (struct link_map
*) map
;
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. */
333 __attribute_noinline__
334 do_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
)
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
;
350 const struct link_map
*map
= list
[i
]->l_real
;
352 /* Here come the extra test needed for `_dl_lookup_symbol_skip'. */
356 /* Don't search the executable when resolving a copy reloc. */
357 if ((type_class
& ELF_RTYPE_CLASS_COPY
) && map
->l_type
== lt_executable
)
360 /* Do not look into objects which are going to be removed. */
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
),
370 /* If the hash table is empty there is nothing to do here. */
371 if (map
->l_nbuckets
== 0)
375 int num_versions
= 0;
376 const ElfW(Sym
) *versioned_sym
= NULL
;
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
]);
382 const ElfW(Sym
) *sym
;
383 const ElfW(Addr
) *bitmask
= map
->l_gnu_bitmask
;
384 if (__glibc_likely (bitmask
!= NULL
))
386 ElfW(Addr
) bitmask_word
387 = bitmask
[(new_hash
/ __ELF_NATIVE_CLASS
)
388 & map
->l_gnu_bitmask_idxbits
];
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));
394 if (__glibc_unlikely ((bitmask_word
>> hashbit1
)
395 & (bitmask_word
>> hashbit2
) & 1))
397 Elf32_Word bucket
= map
->l_gnu_buckets
[new_hash
401 const Elf32_Word
*hasharr
= &map
->l_gnu_chain_zero
[bucket
];
404 if (((*hasharr
^ new_hash
) >> 1) == 0)
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
,
414 while ((*hasharr
++ & 1u) == 0);
417 /* No symbol found. */
422 if (*old_hash
== 0xffffffff)
423 *old_hash
= _dl_elf_hash (undef_name
);
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
];
430 symidx
= map
->l_chain
[symidx
])
432 sym
= check_match (undef_name
, ref
, version
, flags
,
433 type_class
, &symtab
[symidx
], symidx
,
434 strtab
, map
, &versioned_sym
,
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
;
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
455 && map
->l_type
== lt_executable
456 && type_class
== ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
)
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)
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
);
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
)
475 s
= &symtab
[ELFW(R_SYM
) (rela
->r_info
)];
476 if (!strcmp (strtab
+ s
->st_name
, undef_name
))
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)
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
);
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
)
495 s
= &symtab
[ELFW(R_SYM
) (rel
->r_info
)];
496 if (!strcmp (strtab
+ s
->st_name
, undef_name
))
503 /* Hidden and internal symbols are local, ignore them. */
504 if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym
)))
507 switch (ELFW(ST_BIND
) (sym
->st_info
))
510 /* Weak definition. Use this value if we don't find another. */
511 if (__glibc_unlikely (GLRO(dl_dynamic_weak
)))
516 result
->m
= (struct link_map
*) map
;
522 /* Global definition. Just what we need. */
524 result
->m
= (struct link_map
*) map
;
527 case STB_GNU_UNIQUE
:;
528 do_lookup_unique (undef_name
, new_hash
, map
, result
, type_class
,
529 sym
, strtab
, ref
, undef_map
);
533 /* Local symbols are ignored. */
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
)))
547 /* We have not found anything until now. */
553 dl_new_hash (const char *s
)
555 uint_fast32_t h
= 5381;
556 for (unsigned char c
= *s
; c
!= '\0'; c
= *++s
)
558 return h
& 0xffffffff;
562 /* Add extra dependency on MAP to UNDEF_MAP. */
564 add_dependency (struct link_map
*undef_map
, struct link_map
*map
, int flags
)
566 struct link_map
*runp
;
570 /* Avoid self-references and references to objects which cannot be
572 if (undef_map
== map
)
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)
580 struct link_map_reldeps
*l_reldeps
581 = atomic_forced_read (undef_map
->l_reldeps
);
583 /* Make sure l_reldeps is read before l_initfini. */
584 atomic_read_barrier ();
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
)
591 for (i
= 0; l_initfini
[i
] != NULL
; ++i
)
592 if (l_initfini
[i
] == map
)
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
)
601 struct link_map
**list
= &l_reldeps
->list
[0];
602 l_reldepsact
= l_reldeps
->act
;
603 for (i
= 0; i
< l_reldepsact
; ++i
)
608 /* Save serial number of the target MAP. */
609 unsigned long long serial
= map
->l_serial
;
611 /* Make sure nobody can unload the object while we are at it. */
612 if (__glibc_unlikely (flags
& DL_LOOKUP_GSCOPE_LOCK
))
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
);
624 /* From this point on it is unsafe to dereference MAP, until it
625 has been found in one of the lists. */
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
)
632 l_initfini
= undef_map
->l_initfini
;
633 for (i
= 0; l_initfini
[i
] != NULL
; ++i
)
634 if (l_initfini
[i
] == map
)
638 /* Redo the l_reldeps check if undef_map's l_reldeps changed in
640 if (undef_map
->l_reldeps
!= NULL
)
642 if (undef_map
->l_reldeps
!= l_reldeps
)
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
)
650 else if (undef_map
->l_reldeps
->act
> l_reldepsact
)
652 struct link_map
**list
653 = &undef_map
->l_reldeps
->list
[0];
655 l_reldepsact
= undef_map
->l_reldeps
->act
;
656 for (; i
< l_reldepsact
; ++i
)
663 __rtld_lock_lock_recursive (GL(dl_load_lock
));
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
670 runp
= GL(dl_ns
)[undef_map
->l_ns
]._ns_loaded
;
671 while (runp
!= NULL
&& runp
!= map
)
676 /* The object is still available. */
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
)
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)
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
691 if (undef_map
->l_type
!= lt_loaded
692 || (undef_map
->l_flags_1
& DF_1_NODELETE
) != 0)
694 map
->l_flags_1
|= DF_1_NODELETE
;
698 /* Add the reference now. */
699 if (__glibc_unlikely (l_reldepsact
>= undef_map
->l_reldepsmax
))
701 /* Allocate more memory for the dependency list. Since this
702 can never happen during the startup phase we can use
704 struct link_map_reldeps
*newp
;
706 = undef_map
->l_reldepsmax
? undef_map
->l_reldepsmax
* 2 : 10;
708 #ifdef RTLD_PREPARE_FOREIGN_CALL
709 RTLD_PREPARE_FOREIGN_CALL
;
712 newp
= malloc (sizeof (*newp
) + max
* sizeof (struct link_map
*));
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
719 map
->l_flags_1
|= DF_1_NODELETE
;
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
;
734 _dl_scope_free (old
);
739 undef_map
->l_reldeps
->list
[l_reldepsact
] = map
;
740 atomic_write_barrier ();
741 undef_map
->l_reldeps
->act
= l_reldepsact
+ 1;
744 /* Display information if we are debugging. */
745 if (__glibc_unlikely (GLRO(dl_debug_mask
) & DL_DEBUG_FILES
))
747 \nfile=%s [%lu]; needed by %s [%lu] (relocation dependency)\n\n",
748 DSO_FILENAME (map
->l_name
),
750 DSO_FILENAME (undef_map
->l_name
),
754 /* Whoa, that was bad luck. We have to search again. */
758 /* Release the lock. */
759 __rtld_lock_unlock_recursive (GL(dl_load_lock
));
761 if (__glibc_unlikely (flags
& DL_LOOKUP_GSCOPE_LOCK
))
762 THREAD_GSCOPE_SET_FLAG ();
767 if (map
->l_serial
!= serial
)
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
,
779 /* Search loaded objects' symbol tables for a definition of the symbol
780 UNDEF_NAME, perhaps with a requested version for the symbol.
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. */
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
)
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
;
797 bump_num_relocations ();
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
))
806 if (__glibc_unlikely (skip_map
!= NULL
))
807 /* Search the relevant loaded objects for a definition. */
808 while ((*scope
)->r_list
[i
] != skip_map
)
811 /* Search the relevant loaded objects for a definition. */
812 for (size_t start
= i
; *scope
!= NULL
; start
= 0, ++scope
)
814 int res
= do_lookup_x (undef_name
, new_hash
, &old_hash
, *ref
,
815 ¤t_value
, *scope
, start
, version
, flags
,
816 skip_map
, type_class
, undef_map
);
820 if (__glibc_unlikely (res
< 0) && skip_map
== NULL
)
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
);
842 if (__glibc_unlikely (current_value
.s
== NULL
))
844 if ((*ref
== NULL
|| ELFW(ST_BIND
) ((*ref
)->st_info
) != STB_WEAK
)
845 && !(GLRO(dl_debug_mask
) & DL_DEBUG_UNUSED
))
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
);
865 int protected = (*ref
866 && ELFW(ST_VISIBILITY
) ((*ref
)->st_other
) == STV_PROTECTED
);
867 if (__glibc_unlikely (protected != 0))
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
)
873 if (current_value
.s
!= NULL
&& current_value
.m
!= undef_map
)
875 current_value
.s
= *ref
;
876 current_value
.m
= undef_map
;
881 struct sym_val protected_value
= { NULL
, NULL
};
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
,
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)
894 if (protected_value
.s
!= NULL
&& protected_value
.m
!= undef_map
)
896 current_value
.s
= *ref
;
897 current_value
.m
= undef_map
;
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
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
);
919 /* The object is used. */
920 if (__glibc_unlikely (current_value
.m
->l_used
== 0))
921 current_value
.m
->l_used
= 1;
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 ¤t_value
, version
, type_class
, protected);
928 *ref
= current_value
.s
;
929 return LOOKUP_VALUE (current_value
.m
);
933 /* Cache the location of MAP's hash table. */
936 _dl_setup_hash (struct link_map
*map
)
940 if (__glibc_likely (map
->l_info
[ADDRIDX (DT_GNU_HASH
)] != NULL
))
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
++;
952 map
->l_gnu_bitmask
= (ElfW(Addr
) *) hash32
;
953 hash32
+= __ELF_NATIVE_CLASS
/ 32 * bitmask_nwords
;
955 map
->l_gnu_buckets
= hash32
;
956 hash32
+= map
->l_nbuckets
;
957 map
->l_gnu_chain_zero
= hash32
- symbias
;
961 if (!map
->l_info
[DT_HASH
])
963 hash
= (void *) D_PTR (map
, l_info
[DT_HASH
]);
965 map
->l_nbuckets
= *hash
++;
968 map
->l_buckets
= hash
;
969 hash
+= map
->l_nbuckets
;
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
,
980 const char *reference_name
= undef_map
->l_name
;
982 if (GLRO(dl_debug_mask
) & DL_DEBUG_BINDINGS
)
984 _dl_debug_printf ("binding file %s [%lu] to %s [%lu]: %s symbol `%s'",
985 DSO_FILENAME (reference_name
),
987 DSO_FILENAME (value
->m
->l_name
),
989 protected ? "protected" : "normal", undef_name
);
991 _dl_debug_printf_c (" [%s]\n", version
->name
);
993 _dl_debug_printf_c ("\n");
996 if (GLRO(dl_debug_mask
) & DL_DEBUG_PRELINK
)
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!
1007 #if ELF_RTYPE_CLASS_COPY != 0 && ELF_RTYPE_CLASS_COPY != 2
1008 # error ELF_RTYPE_CLASS_COPY must be 0 or 2!
1011 struct sym_val val
= { NULL
, NULL
};
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
)
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
;
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
)
1028 else if (__glibc_unlikely (undef_map
->l_symbolic_in_local_scope
)
1030 && __glibc_unlikely (ELFW(ST_BIND
) (val
.s
->st_info
)
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
};
1041 struct r_scope_elem
*scope
= undef_map
->l_local_scope
[0];
1043 for (n
= 0; n
< scope
->r_nlist
; n
++)
1044 if (scope
->r_list
[n
] == val
.m
)
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
,
1051 &scope
->r_list
[n
]->l_symbolic_searchlist
,
1052 0, version
, 0, NULL
, type_class
,
1060 GL(dl_ns
)[LM_ID_BASE
]._ns_unique_sym_table
.entries
= saved_entries
;
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
)
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
)
1074 /* Set the RTYPE_CLASS_VALID bit. */
1075 type_class
|= RTYPE_CLASS_VALID
;
1079 || GLRO(dl_trace_prelink_map
) == undef_map
1080 || GLRO(dl_trace_prelink_map
) == NULL
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));
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));
1101 _dl_printf ("/%x %s\n", type_class
, undef_name
);