/* Manage TLS descriptors.  i386 version.

   Copyright (C) 2005-2018 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

   <http://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

}