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/* Manage TLS descriptors. x86_64 version.
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Copyright (C) 2005-2018 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 <link.h>
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#include <ldsodefs.h>
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#include <elf/dynamic-link.h>
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#include <tls.h>
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#include <dl-tlsdesc.h>
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#include <dl-unmap-segments.h>
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#include <tlsdeschtab.h>
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/* The following 2 functions take a caller argument, that contains the
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address expected to be in the TLS descriptor. If it's changed, we
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want to return immediately. */
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/* This function is used to lazily resolve TLS_DESC RELA relocations.
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The argument location is used to hold a pointer to the relocation. */
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void
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attribute_hidden
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_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
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struct link_map *l)
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{
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const ElfW(Rela) *reloc = td->arg;
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if (_dl_tlsdesc_resolve_early_return_p
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(td, (void*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_PLT)]) + l->l_addr)))
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return;
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/* The code below was borrowed from _dl_fixup(). */
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const ElfW(Sym) *const symtab
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= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
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const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
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const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
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lookup_t result;
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/* Look up the target symbol. If the normal lookup rules are not
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used don't look in the global scope. */
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if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL
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&& __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
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{
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const struct r_found_version *version = NULL;
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if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
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{
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const ElfW(Half) *vernum =
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(const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
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ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
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version = &l->l_versions[ndx];
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if (version->hash == 0)
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version = NULL;
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}
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result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
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l->l_scope, version, ELF_RTYPE_CLASS_PLT,
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DL_LOOKUP_ADD_DEPENDENCY, NULL);
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}
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else
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{
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/* We already found the symbol. The module (and therefore its load
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address) is also known. */
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result = l;
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}
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if (! sym)
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{
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td->arg = (void*)reloc->r_addend;
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td->entry = _dl_tlsdesc_undefweak;
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}
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else
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{
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# ifndef SHARED
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CHECK_STATIC_TLS (l, result);
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# else
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if (!TRY_STATIC_TLS (l, result))
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{
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td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value
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+ reloc->r_addend);
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td->entry = _dl_tlsdesc_dynamic;
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}
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else
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# endif
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{
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td->arg = (void*)(sym->st_value - result->l_tls_offset
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+ reloc->r_addend);
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td->entry = _dl_tlsdesc_return;
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}
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}
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_dl_tlsdesc_wake_up_held_fixups ();
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}
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/* This function is used to avoid busy waiting for other threads to
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complete the lazy relocation. Once another thread wins the race to
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relocate a TLS descriptor, it sets the descriptor up such that this
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function is called to wait until the resolver releases the
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lock. */
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void
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attribute_hidden
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_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td,
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void *caller)
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{
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/* Maybe we're lucky and can return early. */
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if (caller != td->entry)
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return;
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/* Locking here will stop execution until the running resolver runs
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_dl_tlsdesc_wake_up_held_fixups(), releasing the lock.
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FIXME: We'd be better off waiting on a condition variable, such
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that we didn't have to hold the lock throughout the relocation
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processing. */
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__rtld_lock_lock_recursive (GL(dl_load_lock));
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__rtld_lock_unlock_recursive (GL(dl_load_lock));
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}
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/* Unmap the dynamic object, but also release its TLS descriptor table
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if there is one. */
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void
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_dl_unmap (struct link_map *map)
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{
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_dl_unmap_segments (map);
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#ifdef SHARED
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/* _dl_unmap is only called for dlopen()ed libraries, for which
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calling free() is safe, or before we've completed the initial
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relocation, in which case calling free() is probably pointless,
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but still safe. */
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if (map->l_mach.tlsdesc_table)
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htab_delete (map->l_mach.tlsdesc_table);
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#endif
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}
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