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glibc/elf/dl-lookup.c
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/* Look up a symbol in the loaded objects. | |
Copyright (C) 1995,96,97,98,99,2000 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Library General Public License as | |
published by the Free Software Foundation; either version 2 of the | |
License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Library General Public License for more details. | |
You should have received a copy of the GNU Library General Public | |
License along with the GNU C Library; see the file COPYING.LIB. If not, | |
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
Boston, MA 02111-1307, USA. */ | |
#include <alloca.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include <unistd.h> | |
#include <ldsodefs.h> | |
#include "dl-hash.h" | |
#include <dl-machine.h> | |
#include <bits/libc-lock.h> | |
#include <assert.h> | |
#define VERSTAG(tag) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag)) | |
/* We need this string more than once. */ | |
static const char undefined_msg[] = "undefined symbol: "; | |
struct sym_val | |
{ | |
const ElfW(Sym) *s; | |
struct link_map *m; | |
}; | |
#define make_string(string, rest...) \ | |
({ \ | |
const char *all[] = { string, ## rest }; \ | |
size_t len, cnt; \ | |
char *result, *cp; \ | |
\ | |
len = 1; \ | |
for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \ | |
len += strlen (all[cnt]); \ | |
\ | |
cp = result = alloca (len); \ | |
for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \ | |
cp = __stpcpy (cp, all[cnt]); \ | |
\ | |
result; \ | |
}) | |
/* Statistics function. */ | |
unsigned long int _dl_num_relocations; | |
/* During the program run we must not modify the global data of | |
loaded shared object simultanously in two threads. Therefore we | |
protect `_dl_open' and `_dl_close' in dl-close.c. | |
This must be a recursive lock since the initializer function of | |
the loaded object might as well require a call to this function. | |
At this time it is not anymore a problem to modify the tables. */ | |
__libc_lock_define (extern, _dl_load_lock) | |
/* We have two different situations when looking up a simple: with or | |
without versioning. gcc is not able to optimize a single function | |
definition serving for both purposes so we define two functions. */ | |
#define VERSIONED 0 | |
#define PROTECTED 0 | |
#include "do-lookup.h" | |
#define VERSIONED 1 | |
#define PROTECTED 0 | |
#include "do-lookup.h" | |
/* Add extra dependency on MAP to UNDEF_MAP. */ | |
static int | |
add_dependency (struct link_map *undef_map, struct link_map *map) | |
{ | |
struct link_map **list; | |
unsigned int act; | |
unsigned int i; | |
int result = 0; | |
/* Make sure nobody can unload the object while we are at it. */ | |
__libc_lock_lock (_dl_load_lock); | |
/* Determine whether UNDEF_MAP already has a reference to MAP. First | |
look in the normal dependencies. */ | |
list = undef_map->l_searchlist.r_list; | |
act = undef_map->l_searchlist.r_nlist; | |
for (i = 0; i < act; ++i) | |
if (list[i] == map) | |
break; | |
if (__builtin_expect (i == act, 1)) | |
{ | |
/* No normal dependency. See whether we already had to add it | |
to the special list of dynamic dependencies. */ | |
list = undef_map->l_reldeps; | |
act = undef_map->l_reldepsact; | |
for (i = 0; i < act; ++i) | |
if (list[i] == map) | |
break; | |
if (i == act) | |
{ | |
/* The object is not yet in the dependency list. Before we add | |
it make sure just one more time the object we are about to | |
reference is still available. There is a brief period in | |
which the object could have been removed since we found the | |
definition. */ | |
struct link_map *runp = _dl_loaded; | |
while (runp != NULL && runp != map) | |
runp = runp->l_next; | |
if (runp != NULL) | |
{ | |
/* The object is still available. Add the reference now. */ | |
if (__builtin_expect (act >= undef_map->l_reldepsmax, 0)) | |
{ | |
/* Allocate more memory for the dependency list. Since | |
this can never happen during the startup phase we can | |
use `realloc'. */ | |
void *newp; | |
undef_map->l_reldepsmax += 5; | |
newp = realloc (undef_map->l_reldeps, | |
undef_map->l_reldepsmax | |
* sizeof(struct link_map *)); | |
if (__builtin_expect (newp != NULL, 1)) | |
undef_map->l_reldeps = (struct link_map **) newp; | |
else | |
/* Correct the addition. */ | |
undef_map->l_reldepsmax -= 5; | |
} | |
/* If we didn't manage to allocate memory for the list this | |
is no fatal mistake. We simply increment the use counter | |
of the referenced object and don't record the dependencies. | |
This means this increment can never be reverted and the | |
object will never be unloaded. This is semantically the | |
correct behaviour. */ | |
if (__builtin_expect (act < undef_map->l_reldepsmax, 1)) | |
undef_map->l_reldeps[undef_map->l_reldepsact++] = map; | |
/* And increment the counter in the referenced object. */ | |
++map->l_opencount; | |
/* Display information if we are debugging. */ | |
if (__builtin_expect (_dl_debug_files, 0)) | |
_dl_debug_message (1, "\nfile=", | |
map->l_name[0] ? map->l_name : _dl_argv[0], | |
"; needed by ", | |
undef_map->l_name[0] | |
? undef_map->l_name : _dl_argv[0], | |
" (relocation dependency)\n\n", NULL); | |
} | |
else | |
/* Whoa, that was bad luck. We have to search again. */ | |
result = -1; | |
} | |
} | |
/* Release the lock. */ | |
__libc_lock_unlock (_dl_load_lock); | |
return result; | |
} | |
/* Search loaded objects' symbol tables for a definition of the symbol | |
UNDEF_NAME. */ | |
lookup_t | |
internal_function | |
_dl_lookup_symbol (const char *undef_name, struct link_map *undef_map, | |
const ElfW(Sym) **ref, struct r_scope_elem *symbol_scope[], | |
int reloc_type, int explicit) | |
{ | |
const char *reference_name = undef_map ? undef_map->l_name : NULL; | |
const unsigned long int hash = _dl_elf_hash (undef_name); | |
struct sym_val current_value = { NULL, NULL }; | |
struct r_scope_elem **scope; | |
int protected; | |
int noexec = elf_machine_lookup_noexec_p (reloc_type); | |
int noplt = elf_machine_lookup_noplt_p (reloc_type); | |
++_dl_num_relocations; | |
/* Search the relevant loaded objects for a definition. */ | |
for (scope = symbol_scope; *scope; ++scope) | |
if (do_lookup (undef_name, hash, *ref, ¤t_value, *scope, 0, NULL, | |
noexec, noplt)) | |
{ | |
/* We have to check whether this would bind UNDEF_MAP to an object | |
in the global scope which was dynamically loaded. In this case | |
we have to prevent the latter from being unloaded unless the | |
UNDEF_MAP object is also unloaded. */ | |
if (__builtin_expect (current_value.m->l_global, 0) | |
&& (__builtin_expect (current_value.m->l_type, lt_library) | |
== lt_loaded) | |
&& undef_map != current_value.m | |
/* Don't do this for explicit lookups as opposed to implicit | |
runtime lookups. */ | |
&& __builtin_expect (! explicit, 1) | |
/* Add UNDEF_MAP to the dependencies. */ | |
&& add_dependency (undef_map, current_value.m) < 0) | |
/* Something went wrong. Perhaps the object we tried to reference | |
was just removed. Try finding another definition. */ | |
return _dl_lookup_symbol (undef_name, undef_map, ref, symbol_scope, | |
reloc_type, 0); | |
break; | |
} | |
if (__builtin_expect (current_value.s == NULL, 0)) | |
{ | |
if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK) | |
/* We could find no value for a strong reference. */ | |
/* XXX We cannot translate the messages. */ | |
_dl_signal_cerror (0, (reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), | |
make_string (undefined_msg, undef_name)); | |
*ref = NULL; | |
return 0; | |
} | |
protected = *ref && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED; | |
if (__builtin_expect (_dl_debug_bindings, 0)) | |
_dl_debug_message (1, "binding file ", | |
(reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), | |
" to ", current_value.m->l_name[0] | |
? current_value.m->l_name : _dl_argv[0], | |
": ", protected ? "protected" : "normal", | |
" symbol `", undef_name, "'\n", NULL); | |
if (__builtin_expect (protected == 0, 1)) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
else | |
{ | |
/* It is very tricky. We need to figure out what value to | |
return for the protected symbol */ | |
struct sym_val protected_value = { NULL, NULL }; | |
for (scope = symbol_scope; *scope; ++scope) | |
if (do_lookup (undef_name, hash, *ref, &protected_value, *scope, 0, | |
NULL, 0, 1)) | |
break; | |
if (protected_value.s == NULL || protected_value.m == undef_map) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
return LOOKUP_VALUE (undef_map); | |
} | |
} | |
/* This function is nearly the same as `_dl_lookup_symbol' but it | |
skips in the first list all objects until SKIP_MAP is found. I.e., | |
it only considers objects which were loaded after the described | |
object. If there are more search lists the object described by | |
SKIP_MAP is only skipped. */ | |
lookup_t | |
internal_function | |
_dl_lookup_symbol_skip (const char *undef_name, | |
struct link_map *undef_map, const ElfW(Sym) **ref, | |
struct r_scope_elem *symbol_scope[], | |
struct link_map *skip_map) | |
{ | |
const char *reference_name = undef_map ? undef_map->l_name : NULL; | |
const unsigned long int hash = _dl_elf_hash (undef_name); | |
struct sym_val current_value = { NULL, NULL }; | |
struct r_scope_elem **scope; | |
size_t i; | |
int protected; | |
++_dl_num_relocations; | |
/* Search the relevant loaded objects for a definition. */ | |
scope = symbol_scope; | |
for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i) | |
assert (i < (*scope)->r_nduplist); | |
while (i >= (*scope)->r_nlist | |
|| ! do_lookup (undef_name, hash, *ref, ¤t_value, *scope, i, | |
skip_map, 0, 0)) | |
while (*++scope) | |
if (do_lookup (undef_name, hash, *ref, ¤t_value, *scope, 0, | |
skip_map, 0, 0)) | |
break; | |
if (__builtin_expect (current_value.s == NULL, 0)) | |
{ | |
*ref = NULL; | |
return 0; | |
} | |
protected = *ref && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED; | |
if (__builtin_expect (_dl_debug_bindings, 0)) | |
_dl_debug_message (1, "binding file ", | |
(reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), | |
" to ", current_value.m->l_name[0] | |
? current_value.m->l_name : _dl_argv[0], | |
": ", protected ? "protected" : "normal", | |
" symbol `", undef_name, "'\n", NULL); | |
if (__builtin_expect (protected == 0, 1)) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
else | |
{ | |
/* It is very tricky. We need to figure out what value to | |
return for the protected symbol. */ | |
struct sym_val protected_value = { NULL, NULL }; | |
if (i >= (*scope)->r_nlist | |
|| !do_lookup (undef_name, hash, *ref, &protected_value, *scope, i, | |
skip_map, 0, 1)) | |
while (*++scope) | |
if (do_lookup (undef_name, hash, *ref, &protected_value, *scope, 0, | |
skip_map, 0, 1)) | |
break; | |
if (protected_value.s == NULL || protected_value.m == undef_map) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
return LOOKUP_VALUE (undef_map); | |
} | |
} | |
/* This function works like _dl_lookup_symbol but it takes an | |
additional arguement with the version number of the requested | |
symbol. | |
XXX We'll see whether we need this separate function. */ | |
lookup_t | |
internal_function | |
_dl_lookup_versioned_symbol (const char *undef_name, | |
struct link_map *undef_map, const ElfW(Sym) **ref, | |
struct r_scope_elem *symbol_scope[], | |
const struct r_found_version *version, | |
int reloc_type, int explicit) | |
{ | |
const char *reference_name = undef_map ? undef_map->l_name : NULL; | |
const unsigned long int hash = _dl_elf_hash (undef_name); | |
struct sym_val current_value = { NULL, NULL }; | |
struct r_scope_elem **scope; | |
int protected; | |
int noexec = elf_machine_lookup_noexec_p (reloc_type); | |
int noplt = elf_machine_lookup_noplt_p (reloc_type); | |
++_dl_num_relocations; | |
/* Search the relevant loaded objects for a definition. */ | |
for (scope = symbol_scope; *scope; ++scope) | |
{ | |
int res = do_lookup_versioned (undef_name, hash, *ref, ¤t_value, | |
*scope, 0, version, NULL, noexec, noplt); | |
if (res > 0) | |
{ | |
/* We have to check whether this would bind UNDEF_MAP to an object | |
in the global scope which was dynamically loaded. In this case | |
we have to prevent the latter from being unloaded unless the | |
UNDEF_MAP object is also unloaded. */ | |
if (__builtin_expect (current_value.m->l_global, 0) | |
&& (__builtin_expect (current_value.m->l_type, lt_library) | |
== lt_loaded) | |
&& undef_map != current_value.m | |
/* Don't do this for explicit lookups as opposed to implicit | |
runtime lookups. */ | |
&& __builtin_expect (! explicit, 1) | |
/* Add UNDEF_MAP to the dependencies. */ | |
&& add_dependency (undef_map, current_value.m) < 0) | |
/* Something went wrong. Perhaps the object we tried to reference | |
was just removed. Try finding another definition. */ | |
return _dl_lookup_versioned_symbol (undef_name, undef_map, ref, | |
symbol_scope, version, | |
reloc_type, 0); | |
break; | |
} | |
if (__builtin_expect (res, 0) < 0) | |
{ | |
/* Oh, oh. The file named in the relocation entry does not | |
contain the needed symbol. */ | |
/* XXX We cannot translate the message. */ | |
_dl_signal_cerror (0, (reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), | |
make_string ("symbol ", undef_name, ", version ", | |
version->name, | |
" not defined in file ", | |
version->filename, | |
" with link time reference", | |
res == -2 | |
? " (no version symbols)" : "")); | |
*ref = NULL; | |
return 0; | |
} | |
} | |
if (__builtin_expect (current_value.s == NULL, 0)) | |
{ | |
if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK) | |
/* We could find no value for a strong reference. */ | |
/* XXX We cannot translate the message. */ | |
_dl_signal_cerror (0, (reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), | |
make_string (undefined_msg, undef_name, | |
", version ", version->name ?: NULL)); | |
*ref = NULL; | |
return 0; | |
} | |
protected = *ref && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED; | |
if (__builtin_expect (_dl_debug_bindings, 0)) | |
_dl_debug_message (1, "binding file ", | |
(reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), | |
" to ", current_value.m->l_name[0] | |
? current_value.m->l_name : _dl_argv[0], | |
": ", protected ? "protected" : "normal", | |
" symbol `", undef_name, "' [", version->name, | |
"]\n", NULL); | |
if (__builtin_expect (protected == 0, 1)) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
else | |
{ | |
/* It is very tricky. We need to figure out what value to | |
return for the protected symbol */ | |
struct sym_val protected_value = { NULL, NULL }; | |
for (scope = symbol_scope; *scope; ++scope) | |
if (do_lookup_versioned (undef_name, hash, *ref, &protected_value, | |
*scope, 0, version, NULL, 0, 1)) | |
break; | |
if (protected_value.s == NULL || protected_value.m == undef_map) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
return LOOKUP_VALUE (undef_map); | |
} | |
} | |
/* Similar to _dl_lookup_symbol_skip but takes an additional argument | |
with the version we are looking for. */ | |
lookup_t | |
internal_function | |
_dl_lookup_versioned_symbol_skip (const char *undef_name, | |
struct link_map *undef_map, | |
const ElfW(Sym) **ref, | |
struct r_scope_elem *symbol_scope[], | |
const struct r_found_version *version, | |
struct link_map *skip_map) | |
{ | |
const char *reference_name = undef_map ? undef_map->l_name : NULL; | |
const unsigned long int hash = _dl_elf_hash (undef_name); | |
struct sym_val current_value = { NULL, NULL }; | |
struct r_scope_elem **scope; | |
size_t i; | |
int protected; | |
++_dl_num_relocations; | |
/* Search the relevant loaded objects for a definition. */ | |
scope = symbol_scope; | |
for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i) | |
assert (i < (*scope)->r_nduplist); | |
if (i >= (*scope)->r_nlist | |
|| ! do_lookup_versioned (undef_name, hash, *ref, ¤t_value, | |
*scope, i, version, skip_map, 0, 0)) | |
while (*++scope) | |
if (do_lookup_versioned (undef_name, hash, *ref, ¤t_value, *scope, | |
0, version, skip_map, 0, 0)) | |
break; | |
if (__builtin_expect (current_value.s == NULL, 0)) | |
{ | |
if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK) | |
{ | |
/* We could find no value for a strong reference. */ | |
const size_t len = strlen (undef_name); | |
char buf[sizeof undefined_msg + len]; | |
__mempcpy (__mempcpy (buf, undefined_msg, sizeof undefined_msg - 1), | |
undef_name, len + 1); | |
/* XXX We cannot translate the messages. */ | |
_dl_signal_cerror (0, (reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), buf); | |
} | |
*ref = NULL; | |
return 0; | |
} | |
protected = *ref && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED; | |
if (__builtin_expect (_dl_debug_bindings, 0)) | |
_dl_debug_message (1, "binding file ", | |
(reference_name && reference_name[0] | |
? reference_name | |
: (_dl_argv[0] ?: "<main program>")), | |
" to ", current_value.m->l_name[0] | |
? current_value.m->l_name : _dl_argv[0], | |
": ", protected ? "protected" : "normal", | |
" symbol `", undef_name, "' [", version->name, | |
"]\n", NULL); | |
if (__builtin_expect (protected == 0, 1)) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
else | |
{ | |
/* It is very tricky. We need to figure out what value to | |
return for the protected symbol */ | |
struct sym_val protected_value = { NULL, NULL }; | |
if (i >= (*scope)->r_nlist | |
|| !do_lookup_versioned (undef_name, hash, *ref, &protected_value, | |
*scope, i, version, skip_map, 0, 1)) | |
while (*++scope) | |
if (do_lookup_versioned (undef_name, hash, *ref, &protected_value, | |
*scope, 0, version, skip_map, 0, 1)) | |
break; | |
if (protected_value.s == NULL || protected_value.m == undef_map) | |
{ | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
return LOOKUP_VALUE (undef_map); | |
} | |
} | |
/* Cache the location of MAP's hash table. */ | |
void | |
internal_function | |
_dl_setup_hash (struct link_map *map) | |
{ | |
Elf_Symndx *hash; | |
Elf_Symndx nchain; | |
if (!map->l_info[DT_HASH]) | |
return; | |
hash = (void *)(map->l_addr + map->l_info[DT_HASH]->d_un.d_ptr); | |
map->l_nbuckets = *hash++; | |
nchain = *hash++; | |
map->l_buckets = hash; | |
hash += map->l_nbuckets; | |
map->l_chain = hash; | |
} |