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/* Look up a symbol in a shared object loaded by `dlopen'.
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Copyright (C) 1999-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <stddef.h>
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#include <setjmp.h>
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#include <stdlib.h>
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#include <libintl.h>
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#include <dlfcn.h>
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#include <ldsodefs.h>
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#include <dl-hash.h>
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#include <sysdep-cancel.h>
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#include <dl-tls.h>
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#include <dl-irel.h>
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#ifdef SHARED
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/* Systems which do not have tls_index also probably have to define
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DONT_USE_TLS_INDEX. */
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# ifndef __TLS_GET_ADDR
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# define __TLS_GET_ADDR __tls_get_addr
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# endif
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/* Return the symbol address given the map of the module it is in and
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the symbol record. This is used in dl-sym.c. */
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static void *
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_dl_tls_symaddr (struct link_map *map, const ElfW(Sym) *ref)
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{
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# ifndef DONT_USE_TLS_INDEX
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tls_index tmp =
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{
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.ti_module = map->l_tls_modid,
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.ti_offset = ref->st_value
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};
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return __TLS_GET_ADDR (&tmp);
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# else
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return __TLS_GET_ADDR (map->l_tls_modid, ref->st_value);
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# endif
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}
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#endif
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struct call_dl_lookup_args
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{
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/* Arguments to do_dlsym. */
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struct link_map *map;
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const char *name;
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struct r_found_version *vers;
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int flags;
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/* Return values of do_dlsym. */
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lookup_t loadbase;
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const ElfW(Sym) **refp;
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};
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static void
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call_dl_lookup (void *ptr)
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{
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struct call_dl_lookup_args *args = (struct call_dl_lookup_args *) ptr;
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args->map = GLRO(dl_lookup_symbol_x) (args->name, args->map, args->refp,
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args->map->l_scope, args->vers, 0,
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args->flags, NULL);
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}
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static void *
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do_sym (void *handle, const char *name, void *who,
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struct r_found_version *vers, int flags)
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{
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const ElfW(Sym) *ref = NULL;
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lookup_t result;
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ElfW(Addr) caller = (ElfW(Addr)) who;
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struct link_map *l = _dl_find_dso_for_object (caller);
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/* If the address is not recognized the call comes from the main
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program (we hope). */
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struct link_map *match = l ? l : GL(dl_ns)[LM_ID_BASE]._ns_loaded;
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if (handle == RTLD_DEFAULT)
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{
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/* Search the global scope. We have the simple case where
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we look up in the scope of an object which was part of
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the initial binary. And then the more complex part
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where the object is dynamically loaded and the scope
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array can change. */
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if (RTLD_SINGLE_THREAD_P)
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result = GLRO(dl_lookup_symbol_x) (name, match, &ref,
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match->l_scope, vers, 0,
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flags | DL_LOOKUP_ADD_DEPENDENCY,
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NULL);
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else
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{
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struct call_dl_lookup_args args;
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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
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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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struct dl_exception exception;
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int err = _dl_catch_exception (&exception, call_dl_lookup, &args);
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THREAD_GSCOPE_RESET_FLAG ();
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if (__glibc_unlikely (exception.errstring != NULL))
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_dl_signal_exception (err, &exception, NULL);
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result = args.map;
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}
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}
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else if (handle == RTLD_NEXT)
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{
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if (__glibc_unlikely (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded))
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{
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if (match == NULL
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|| caller < match->l_map_start
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|| caller >= match->l_map_end)
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_dl_signal_error (0, NULL, NULL, N_("\
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RTLD_NEXT used in code not dynamically loaded"));
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}
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struct link_map *l = match;
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while (l->l_loader != NULL)
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l = l->l_loader;
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result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope,
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vers, 0, 0, match);
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}
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else
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{
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/* Search the scope of the given object. */
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struct link_map *map = handle;
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result = GLRO(dl_lookup_symbol_x) (name, map, &ref, map->l_local_scope,
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vers, 0, flags, NULL);
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}
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if (ref != NULL)
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{
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void *value;
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#ifdef SHARED
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if (ELFW(ST_TYPE) (ref->st_info) == STT_TLS)
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/* The found symbol is a thread-local storage variable.
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Return the address for to the current thread. */
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value = _dl_tls_symaddr (result, ref);
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else
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#endif
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value = DL_SYMBOL_ADDRESS (result, ref);
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/* Resolve indirect function address. */
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if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC))
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{
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DL_FIXUP_VALUE_TYPE fixup
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= DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value);
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fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup));
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value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup);
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}
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#ifdef SHARED
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/* Auditing checkpoint: we have a new binding. Provide the
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auditing libraries the possibility to change the value and
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tell us whether further auditing is wanted. */
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if (__glibc_unlikely (GLRO(dl_naudit) > 0))
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{
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const char *strtab = (const char *) D_PTR (result,
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l_info[DT_STRTAB]);
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/* Compute index of the symbol entry in the symbol table of
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the DSO with the definition. */
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unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
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l_info[DT_SYMTAB]));
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if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
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{
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unsigned int altvalue = 0;
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struct audit_ifaces *afct = GLRO(dl_audit);
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/* Synthesize a symbol record where the st_value field is
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the result. */
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ElfW(Sym) sym = *ref;
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sym.st_value = (ElfW(Addr)) value;
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for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
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{
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if (afct->symbind != NULL
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&& ((match->l_audit[cnt].bindflags & LA_FLG_BINDFROM)
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!= 0
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|| ((result->l_audit[cnt].bindflags & LA_FLG_BINDTO)
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!= 0)))
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{
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unsigned int flags = altvalue | LA_SYMB_DLSYM;
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uintptr_t new_value
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= afct->symbind (&sym, ndx,
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&match->l_audit[cnt].cookie,
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&result->l_audit[cnt].cookie,
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&flags, strtab + ref->st_name);
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if (new_value != (uintptr_t) sym.st_value)
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{
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altvalue = LA_SYMB_ALTVALUE;
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sym.st_value = new_value;
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}
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}
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afct = afct->next;
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}
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value = (void *) sym.st_value;
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}
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}
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#endif
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return value;
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}
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return NULL;
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}
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void *
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_dl_vsym (void *handle, const char *name, const char *version, void *who)
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{
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struct r_found_version vers;
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/* Compute hash value to the version string. */
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vers.name = version;
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vers.hidden = 1;
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vers.hash = _dl_elf_hash (version);
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/* We don't have a specific file where the symbol can be found. */
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vers.filename = NULL;
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return do_sym (handle, name, who, &vers, 0);
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}
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void *
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_dl_sym (void *handle, const char *name, void *who)
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{
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return do_sym (handle, name, who, NULL, DL_LOOKUP_RETURN_NEWEST);
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}
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