* sysdeps/generic/ldsodefs.h (DL_LOOKUP_GSCOPE_LOCK): New definition.
* elf/dl-runtime.c (_dl_fixup, _dl_profile_fixup): Or in DL_LOOKUP_GSCOPE_LOCK into flags after THREAD_GSCOPE_SET_FLAG (). * elf/dl-sym.c (do_sym): Likewise. * include/link.h (struct link_map): Add l_serial field. * elf/dl-object.c (_dl_new_object): Initialize l_serial. * elf/dl-lookup.c (add_dependency): Add flags argument. Remember map->l_serial, if DL_LOOKUP_GSCOPE_LOCK is among flags, use THREAD_GSCOPE_RESET_FLAG before and THREAD_GSCOPE_SET_FLAG after __rtld_lock_lock_recursive (GL(dl_load_lock)) to avoid deadlock. Don't dereference map until it has been found on some list. If map->l_serial changed, return -1.
This commit is contained in:
Ulrich Drepper
parent
874aa52349
commit
b90395e6e9
16
ChangeLog
16
ChangeLog
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@ -1,3 +1,19 @@
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2007-09-18 Jakub Jelinek <jakub@redhat.com>
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* sysdeps/generic/ldsodefs.h (DL_LOOKUP_GSCOPE_LOCK): New definition.
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* elf/dl-runtime.c (_dl_fixup, _dl_profile_fixup): Or in
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DL_LOOKUP_GSCOPE_LOCK into flags after THREAD_GSCOPE_SET_FLAG ().
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* elf/dl-sym.c (do_sym): Likewise.
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* include/link.h (struct link_map): Add l_serial field.
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* elf/dl-object.c (_dl_new_object): Initialize l_serial.
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* elf/dl-lookup.c (add_dependency): Add flags argument.
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Remember map->l_serial, if DL_LOOKUP_GSCOPE_LOCK is among
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flags, use THREAD_GSCOPE_RESET_FLAG before and
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THREAD_GSCOPE_SET_FLAG after
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__rtld_lock_lock_recursive (GL(dl_load_lock)) to avoid deadlock.
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Don't dereference map until it has been found on some list.
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If map->l_serial changed, return -1.
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2007-09-17 Jakub Jelinek <jakub@redhat.com>
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* include/stdio.h (__isoc99_fscanf, __isoc99_scanf,
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@ -86,36 +86,42 @@ dl_new_hash (const char *s)
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/* Add extra dependency on MAP to UNDEF_MAP. */
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static int
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internal_function
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add_dependency (struct link_map *undef_map, struct link_map *map)
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add_dependency (struct link_map *undef_map, struct link_map *map, int flags)
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{
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struct link_map **list;
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struct link_map *runp;
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unsigned int act;
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unsigned int i;
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int result = 0;
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unsigned long long int serial;
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/* Avoid self-references and references to objects which cannot be
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unloaded anyway. */
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if (undef_map == map)
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return 0;
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/* Save serial number of the target MAP. */
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serial = map->l_serial;
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/* Make sure nobody can unload the object while we are at it. */
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__rtld_lock_lock_recursive (GL(dl_load_lock));
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/* Avoid references to objects which cannot be unloaded anyway. */
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if (map->l_type != lt_loaded
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|| (map->l_flags_1 & DF_1_NODELETE) != 0)
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goto out;
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/* If the object with the undefined reference cannot be removed ever
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just make sure the same is true for the object which contains the
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definition. */
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if (undef_map->l_type != lt_loaded
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|| (undef_map->l_flags_1 & DF_1_NODELETE) != 0)
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if (__builtin_expect (flags & DL_LOOKUP_GSCOPE_LOCK, 0))
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{
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map->l_flags_1 |= DF_1_NODELETE;
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goto out;
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/* We can't just call __rtld_lock_lock_recursive (GL(dl_load_lock))
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here, that can result in ABBA deadlock. */
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THREAD_GSCOPE_RESET_FLAG ();
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__rtld_lock_lock_recursive (GL(dl_load_lock));
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THREAD_GSCOPE_SET_FLAG ();
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/* While MAP value won't change, after THREAD_GSCOPE_RESET_FLAG ()
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it can e.g. point to unallocated memory. So avoid the optimizer
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treating the above read from MAP->l_serial as ensurance it
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can safely dereference it. */
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map = atomic_forced_read (map);
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}
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else
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__rtld_lock_lock_recursive (GL(dl_load_lock));
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/* From this point on it is unsafe to dereference MAP, until it
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has been found in one of the lists. */
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/* Determine whether UNDEF_MAP already has a reference to MAP. First
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look in the normal dependencies. */
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@ -125,7 +131,7 @@ add_dependency (struct link_map *undef_map, struct link_map *map)
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for (i = 0; list[i] != NULL; ++i)
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if (list[i] == map)
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goto out;
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goto out_check;
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}
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/* No normal dependency. See whether we already had to add it
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@ -135,7 +141,7 @@ add_dependency (struct link_map *undef_map, struct link_map *map)
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for (i = 0; i < act; ++i)
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if (list[i] == map)
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goto out;
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goto out_check;
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/* The object is not yet in the dependency list. Before we add
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it make sure just one more time the object we are about to
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@ -148,7 +154,29 @@ add_dependency (struct link_map *undef_map, struct link_map *map)
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if (runp != NULL)
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{
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/* The object is still available. Add the reference now. */
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/* The object is still available. */
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/* MAP could have been dlclosed, freed and then some other dlopened
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library could have the same link_map pointer. */
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if (map->l_serial != serial)
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goto out_check;
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/* Avoid references to objects which cannot be unloaded anyway. */
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if (map->l_type != lt_loaded
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|| (map->l_flags_1 & DF_1_NODELETE) != 0)
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goto out;
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/* If the object with the undefined reference cannot be removed ever
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just make sure the same is true for the object which contains the
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definition. */
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if (undef_map->l_type != lt_loaded
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|| (undef_map->l_flags_1 & DF_1_NODELETE) != 0)
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{
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map->l_flags_1 |= DF_1_NODELETE;
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goto out;
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}
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/* Add the reference now. */
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if (__builtin_expect (act >= undef_map->l_reldepsmax, 0))
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{
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/* Allocate more memory for the dependency list. Since this
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@ -196,6 +224,11 @@ add_dependency (struct link_map *undef_map, struct link_map *map)
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__rtld_lock_unlock_recursive (GL(dl_load_lock));
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return result;
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out_check:
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if (map->l_serial != serial)
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result = -1;
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goto out;
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}
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static void
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@ -227,9 +260,11 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
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bump_num_relocations ();
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/* No other flag than DL_LOOKUP_ADD_DEPENDENCY is allowed if we look
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up a versioned symbol. */
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assert (version == NULL || (flags & ~(DL_LOOKUP_ADD_DEPENDENCY)) == 0);
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/* No other flag than DL_LOOKUP_ADD_DEPENDENCY or DL_LOOKUP_GSCOPE_LOCK
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is allowed if we look up a versioned symbol. */
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assert (version == NULL
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|| (flags & ~(DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK))
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== 0);
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size_t i = 0;
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if (__builtin_expect (skip_map != NULL, 0))
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@ -335,10 +370,12 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
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runtime lookups. */
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&& (flags & DL_LOOKUP_ADD_DEPENDENCY) != 0
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/* Add UNDEF_MAP to the dependencies. */
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&& add_dependency (undef_map, current_value.m) < 0)
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&& add_dependency (undef_map, current_value.m, flags) < 0)
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/* Something went wrong. Perhaps the object we tried to reference
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was just removed. Try finding another definition. */
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return _dl_lookup_symbol_x (undef_name, undef_map, ref, symbol_scope,
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return _dl_lookup_symbol_x (undef_name, undef_map, ref,
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(flags & DL_LOOKUP_GSCOPE_LOCK)
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? undef_map->l_scope : symbol_scope,
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version, type_class, flags, skip_map);
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/* The object is used. */
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@ -103,6 +103,7 @@ _dl_new_object (char *realname, const char *libname, int type,
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else
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GL(dl_ns)[nsid]._ns_loaded = new;
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++GL(dl_ns)[nsid]._ns_nloaded;
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new->l_serial = GL(dl_load_adds);
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++GL(dl_load_adds);
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/* If we have no loader the new object acts as it. */
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@ -100,7 +100,10 @@ _dl_fixup (
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we are not using any threads (yet). */
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int flags = DL_LOOKUP_ADD_DEPENDENCY;
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if (!RTLD_SINGLE_THREAD_P)
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THREAD_GSCOPE_SET_FLAG ();
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{
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THREAD_GSCOPE_SET_FLAG ();
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flags |= DL_LOOKUP_GSCOPE_LOCK;
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}
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result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym, l->l_scope,
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version, ELF_RTYPE_CLASS_PLT, flags, NULL);
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@ -192,7 +195,10 @@ _dl_profile_fixup (
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we are not using any threads (yet). */
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int flags = DL_LOOKUP_ADD_DEPENDENCY;
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if (!RTLD_SINGLE_THREAD_P)
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THREAD_GSCOPE_SET_FLAG ();
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{
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THREAD_GSCOPE_SET_FLAG ();
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flags |= DL_LOOKUP_GSCOPE_LOCK;
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}
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result = _dl_lookup_symbol_x (strtab + refsym->st_name, l,
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&defsym, l->l_scope, version,
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@ -123,7 +123,8 @@ do_sym (void *handle, const char *name, void *who,
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args.name = name;
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args.map = match;
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args.vers = vers;
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args.flags = flags | DL_LOOKUP_ADD_DEPENDENCY;
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args.flags
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= flags | DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK;
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args.refp = &ref;
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THREAD_GSCOPE_SET_FLAG ();
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@ -286,6 +286,8 @@ struct link_map
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ElfW(Addr) l_relro_addr;
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size_t l_relro_size;
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unsigned long long int l_serial;
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/* Audit information. This array apparent must be the last in the
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structure. Never add something after it. */
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struct auditstate
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@ -845,7 +845,9 @@ enum
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DL_LOOKUP_ADD_DEPENDENCY = 1,
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/* Return most recent version instead of default version for
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unversioned lookup. */
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DL_LOOKUP_RETURN_NEWEST = 2
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DL_LOOKUP_RETURN_NEWEST = 2,
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/* Set if dl_lookup* called with GSCOPE lock held. */
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DL_LOOKUP_GSCOPE_LOCK = 4,
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};
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/* Lookup versioned symbol. */
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