dist/bfd/elf-s390-common.c

/* IBM S/390-specific support for ELF 32 and 64 bit functions
   Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
   2011, 2012 Free Software Foundation, Inc.
   Contributed by Andreas Krebbel.

   This file is part of BFD, the Binary File Descriptor library.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
   02110-1301, USA.  */


/* Return TRUE if H is an IFUNC symbol.  Simply checking for the
   symbol type might not be enough since it might get changed to
   STT_FUNC for pointer equality reasons.  */
static inline bfd_boolean
s390_is_ifunc_symbol_p (struct elf_link_hash_entry *h)
{
  struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
  return h->type == STT_GNU_IFUNC || eh->ifunc_resolver_address != 0;
}

/* Create sections needed by STT_GNU_IFUNC symbol.  */

static bfd_boolean
s390_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
{
  flagword flags;
  asection *s;
  const struct elf_backend_data *bed = get_elf_backend_data (abfd);
  struct elf_link_hash_table *htab = elf_hash_table (info);

  if (htab->iplt != NULL)
    return TRUE;

  flags = bed->dynamic_sec_flags;

  if (info->shared)
    {
      s = bfd_make_section_with_flags (abfd, ".rela.ifunc",
				       flags | SEC_READONLY);
      if (s == NULL
	  || ! bfd_set_section_alignment (abfd, s,
					  bed->s->log_file_align))
	return FALSE;
      htab->irelifunc = s;
    }

  /* Create .iplt, .rel[a].iplt, and .igot.plt.  */
  s = bfd_make_section_with_flags (abfd, ".iplt",
				   flags | SEC_CODE | SEC_READONLY);
  if (s == NULL
      || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
    return FALSE;
  htab->iplt = s;

  s = bfd_make_section_with_flags (abfd, ".rela.iplt", flags | SEC_READONLY);
  if (s == NULL
      || ! bfd_set_section_alignment (abfd, s,
				      bed->s->log_file_align))
    return FALSE;
  htab->irelplt = s;

  s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
  if (s == NULL
      || !bfd_set_section_alignment (abfd, s,
				     bed->s->log_file_align))
    return FALSE;
  htab->igotplt = s;

  return TRUE;
}


/* Allocate space in .plt, .got and associated reloc sections for
   dynamic relocs against a STT_GNU_IFUNC symbol definition.  */

static bfd_boolean
s390_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
				    struct elf_link_hash_entry *h,
				    struct elf_dyn_relocs **head)
{
  struct elf_dyn_relocs *p;
  struct elf_link_hash_table *htab;
  struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;

  htab = elf_hash_table (info);
  eh->ifunc_resolver_address = h->root.u.def.value;
  eh->ifunc_resolver_section = h->root.u.def.section;

  /* Support garbage collection against STT_GNU_IFUNC symbols.  */
  if (h->plt.refcount <= 0 && h->got.refcount <= 0)
    {
      /* When building shared library, we need to handle the case
         where it is marked with regular reference, but not non-GOT
	 reference.  It may happen if we didn't see STT_GNU_IFUNC
	 symbol at the time when checking relocations.  */
      if (info->shared
	  && !h->non_got_ref
	  && h->ref_regular)
	for (p = *head; p != NULL; p = p->next)
	  if (p->count)
	    {
	      h->non_got_ref = 1;
	      goto keep;
	    }

      h->got = htab->init_got_offset;
      h->plt = htab->init_plt_offset;
      *head = NULL;
      return TRUE;
    }

  /* Return and discard space for dynamic relocations against it if
     it is never referenced in a non-shared object.  */
  if (!h->ref_regular)
    {
      if (h->plt.refcount > 0
	  || h->got.refcount > 0)
	abort ();
      h->got = htab->init_got_offset;
      h->plt = htab->init_plt_offset;
      *head = NULL;
      return TRUE;
    }

keep:
  /* Without checking h->plt.refcount here we allocate a PLT slot.
     When setting plt.refcount in check_relocs it might not have been
     known that this will be an IFUNC symol.  */
  h->plt.offset = htab->iplt->size;
  h->needs_plt = 1;
  htab->iplt->size += PLT_ENTRY_SIZE;
  htab->igotplt->size += GOT_ENTRY_SIZE;
  htab->irelplt->size += RELA_ENTRY_SIZE;
  htab->irelplt->reloc_count++;

  /* In order to make pointer equality work with IFUNC symbols defined
     in a non-PIE executable and referenced in a shared lib, we turn
     the symbol into a STT_FUNC symbol and make the symbol value to
     point to the IPLT slot.  That way the referencing shared lib will
     always get the PLT slot address when resolving the respective
     R_390_GLOB_DAT/R_390_64 relocs on that symbol.  */
  if (info->executable && !info->shared && h->def_regular && h->ref_dynamic)
    {
      h->root.u.def.section = htab->iplt;
      h->root.u.def.value = h->plt.offset;
      h->size = PLT_ENTRY_SIZE;
      h->type = STT_FUNC;
    }

  /* We need dynamic relocation for STT_GNU_IFUNC symbol only when
     there is a non-GOT reference in a shared object.  */
  if (!info->shared || !h->non_got_ref)
    *head = NULL;

  /* Finally, allocate space.  */
  p = *head;
  if (p != NULL)
    {
      bfd_size_type count = 0;
      do
	{
	  count += p->count;
	  p = p->next;
	}
      while (p != NULL);
      htab->irelifunc->size += count * RELA_ENTRY_SIZE;
    }

  /* Decide whether the got.iplt slot can be used.  This has to be
     avoided if the values in the GOT slots could differ for pointer
     equality reasons.  */
  if (h->got.refcount <= 0
      || (info->shared
	  && (h->dynindx == -1 || h->forced_local))
      || (info->executable && info->shared)
      || htab->sgot == NULL)
    {
      /* Use .got.iplt.  */
      h->got.offset = (bfd_vma) -1;
    }
  else
    {
      h->got.offset = htab->sgot->size;
      htab->sgot->size += GOT_ENTRY_SIZE;
      if (info->shared)
	htab->srelgot->size += RELA_ENTRY_SIZE;
    }

  return TRUE;
}

static bfd_boolean
elf_s390_allocate_local_syminfo (bfd *abfd, Elf_Internal_Shdr *symtab_hdr)
{
  bfd_size_type size;

  size = symtab_hdr->sh_info;
  size *= (sizeof (bfd_signed_vma)       /* local got */
	   + sizeof (struct plt_entry)   /* local plt */
	   + sizeof(char));              /* local tls type */
  elf_local_got_refcounts (abfd) = ((bfd_signed_vma *)
				    bfd_zalloc (abfd, size));
  if (elf_local_got_refcounts (abfd) == NULL)
    return FALSE;
  elf_s390_local_plt (abfd)
    = (struct plt_entry*)(elf_local_got_refcounts (abfd)
			  + symtab_hdr->sh_info);
  elf_s390_local_got_tls_type (abfd)
    = (char *) (elf_s390_local_plt (abfd) + symtab_hdr->sh_info);

  return TRUE;
}

/* Pick ELFOSABI_GNU if IFUNC symbols are used.  */

static bfd_boolean
elf_s390_add_symbol_hook (bfd *abfd,
			  struct bfd_link_info *info,
			  Elf_Internal_Sym *sym,
			  const char **namep ATTRIBUTE_UNUSED,
			  flagword *flagsp ATTRIBUTE_UNUSED,
			  asection **secp ATTRIBUTE_UNUSED,
			  bfd_vma *valp ATTRIBUTE_UNUSED)
{
  if ((abfd->flags & DYNAMIC) == 0
      && ELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC)
    elf_tdata (info->output_bfd)->has_gnu_symbols = TRUE;

  return TRUE;
}