text: /* Manage TLS descriptors.  i386 version.
     Copyright (C) 2005-2020 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 Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 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
     Lesser General Public License for more details.
  
     You should have received a copy of the GNU Lesser General Public
     License along with the GNU C Library; if not, see
     <https://www.gnu.org/licenses/>.  */
  
  #include <link.h>
  #include <ldsodefs.h>
  #include <elf/dynamic-link.h>
  #include <tls.h>
  #include <dl-tlsdesc.h>
  #include <dl-unmap-segments.h>
  #include <tlsdeschtab.h>
  
  /* The following 4 functions take an entry_check_offset argument.
     It's computed by the caller as an offset between its entry point
     and the call site, such that by adding the built-in return address
     that is implicitly passed to the function with this offset, we can
     easily obtain the caller's entry point to compare with the entry
     point given in the TLS descriptor.  If it's changed, we want to
     return immediately.  */
  
  /* This function is used to lazily resolve TLS_DESC REL relocations
     that reference the *ABS* segment in their own link maps.  The
     argument is the addend originally stored there.  */
  
  void
  __attribute__ ((regparm (3))) attribute_hidden
  _dl_tlsdesc_resolve_abs_plus_addend_fixup (struct tlsdesc volatile *td,
  					   struct link_map *l,
  					   ptrdiff_t entry_check_offset)
  {
    ptrdiff_t addend = (ptrdiff_t) td->arg;
  
    if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
  					  - entry_check_offset))
      return;
  
  #ifndef SHARED
    CHECK_STATIC_TLS (l, l);
  #else
    if (!TRY_STATIC_TLS (l, l))
      {
        td->arg = _dl_make_tlsdesc_dynamic (l, addend);
        td->entry = _dl_tlsdesc_dynamic;
      }
    else
  #endif
      {
        td->arg = (void*) (addend - l->l_tls_offset);
        td->entry = _dl_tlsdesc_return;
      }
  
    _dl_tlsdesc_wake_up_held_fixups ();
  }
  
  /* This function is used to lazily resolve TLS_DESC REL relocations
     that originally had zero addends.  The argument location, that
     originally held the addend, is used to hold a pointer to the
     relocation, but it has to be restored before we call the function
     that applies relocations.  */
  
  void
  __attribute__ ((regparm (3))) attribute_hidden
  _dl_tlsdesc_resolve_rel_fixup (struct tlsdesc volatile *td,
  			       struct link_map *l,
  			       ptrdiff_t entry_check_offset)
  {
    const ElfW(Rel) *reloc = td->arg;
  
    if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
  					  - entry_check_offset))
      return;
  
    /* The code below was borrowed from _dl_fixup(),
       except for checking for STB_LOCAL.  */
    const ElfW(Sym) *const symtab
      = (const void *) D_PTR (l, l_info[DT_SYMTAB]);
    const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
    const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
    lookup_t result;
  
     /* Look up the target symbol.  If the normal lookup rules are not
        used don't look in the global scope.  */
    if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL
        && __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
      {
        const struct r_found_version *version = NULL;
  
        if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
  	{
  	  const ElfW(Half) *vernum =
  	    (const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
  	  ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
  	  version = &l->l_versions[ndx];
  	  if (version->hash == 0)
  	    version = NULL;
  	}
  
        result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
  				    l->l_scope, version, ELF_RTYPE_CLASS_PLT,
  				    DL_LOOKUP_ADD_DEPENDENCY, NULL);
      }
    else
      {
        /* We already found the symbol.  The module (and therefore its load
  	 address) is also known.  */
        result = l;
      }
  
    if (!sym)
      {
        td->arg = 0;
        td->entry = _dl_tlsdesc_undefweak;
      }
    else
      {
  #  ifndef SHARED
        CHECK_STATIC_TLS (l, result);
  #  else
        if (!TRY_STATIC_TLS (l, result))
  	{
  	  td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value);
  	  td->entry = _dl_tlsdesc_dynamic;
  	}
        else
  #  endif
  	{
  	  td->arg = (void*)(sym->st_value - result->l_tls_offset);
  	  td->entry = _dl_tlsdesc_return;
  	}
      }
  
    _dl_tlsdesc_wake_up_held_fixups ();
  }
  
  /* This function is used to lazily resolve TLS_DESC RELA relocations.
     The argument location is used to hold a pointer to the relocation.  */
  
  void
  __attribute__ ((regparm (3))) attribute_hidden
  _dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
  				struct link_map *l,
  				ptrdiff_t entry_check_offset)
  {
    const ElfW(Rela) *reloc = td->arg;
  
    if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
  					  - entry_check_offset))
      return;
  
    /* The code below was borrowed from _dl_fixup(),
       except for checking for STB_LOCAL.  */
    const ElfW(Sym) *const symtab
      = (const void *) D_PTR (l, l_info[DT_SYMTAB]);
    const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
    const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
    lookup_t result;
  
     /* Look up the target symbol.  If the normal lookup rules are not
        used don't look in the global scope.  */
    if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL
        && __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
      {
        const struct r_found_version *version = NULL;
  
        if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
  	{
  	  const ElfW(Half) *vernum =
  	    (const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
  	  ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
  	  version = &l->l_versions[ndx];
  	  if (version->hash == 0)
  	    version = NULL;
  	}
  
        result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
  				    l->l_scope, version, ELF_RTYPE_CLASS_PLT,
  				    DL_LOOKUP_ADD_DEPENDENCY, NULL);
      }
    else
      {
        /* We already found the symbol.  The module (and therefore its load
  	 address) is also known.  */
        result = l;
      }
  
    if (!sym)
      {
        td->arg = (void*) reloc->r_addend;
        td->entry = _dl_tlsdesc_undefweak;
      }
    else
      {
  #  ifndef SHARED
        CHECK_STATIC_TLS (l, result);
  #  else
        if (!TRY_STATIC_TLS (l, result))
  	{
  	  td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value
  					      + reloc->r_addend);
  	  td->entry = _dl_tlsdesc_dynamic;
  	}
        else
  #  endif
  	{
  	  td->arg = (void*) (sym->st_value - result->l_tls_offset
  			     + reloc->r_addend);
  	  td->entry = _dl_tlsdesc_return;
  	}
      }
  
    _dl_tlsdesc_wake_up_held_fixups ();
  }
  
  /* This function is used to avoid busy waiting for other threads to
     complete the lazy relocation.  Once another thread wins the race to
     relocate a TLS descriptor, it sets the descriptor up such that this
     function is called to wait until the resolver releases the
     lock.  */
  
  void
  __attribute__ ((regparm (3))) attribute_hidden
  _dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td,
  				struct link_map *l __attribute__((__unused__)),
  				ptrdiff_t entry_check_offset)
  {
    /* Maybe we're lucky and can return early.  */
    if (__builtin_return_address (0) - entry_check_offset != td->entry)
      return;
  
    /* Locking here will stop execution until the running resolver runs
       _dl_tlsdesc_wake_up_held_fixups(), releasing the lock.
  
       FIXME: We'd be better off waiting on a condition variable, such
       that we didn't have to hold the lock throughout the relocation
       processing.  */
    __rtld_lock_lock_recursive (GL(dl_load_lock));
    __rtld_lock_unlock_recursive (GL(dl_load_lock));
  }
  
  
  /* Unmap the dynamic object, but also release its TLS descriptor table
     if there is one.  */
  
  void
  _dl_unmap (struct link_map *map)
  {
    _dl_unmap_segments (map);
  
  #ifdef SHARED
    if (map->l_mach.tlsdesc_table)
      htab_delete (map->l_mach.tlsdesc_table);
  #endif
  }
  