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[/] [openrisc/] [trunk/] [gnu-old/] [gdb-7.1/] [bfd/] [elf-ifunc.c] - Blame information for rev 853

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Line No. Rev Author Line
1 227 jeremybenn
/* ELF STT_GNU_IFUNC support.
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   Copyright 2009
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   Free Software Foundation, Inc.
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   This file is part of BFD, the Binary File Descriptor library.
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   This program is free software; you can redistribute it and/or modify
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   it under the terms of the GNU General Public License as published by
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   the Free Software Foundation; either version 3 of the License, or
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   (at your option) any later version.
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   This program 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
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   GNU General Public License for more details.
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   You should have received a copy of the GNU General Public License
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   along with this program; if not, write to the Free Software
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   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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   MA 02110-1301, USA.  */
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#include "sysdep.h"
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#include "bfd.h"
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#include "bfdlink.h"
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#include "libbfd.h"
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#define ARCH_SIZE 0
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#include "elf-bfd.h"
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#include "safe-ctype.h"
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#include "libiberty.h"
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#include "objalloc.h"
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/* Create sections needed by STT_GNU_IFUNC symbol.  */
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bfd_boolean
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_bfd_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
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{
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  flagword flags, pltflags;
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  asection *s;
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  const struct elf_backend_data *bed = get_elf_backend_data (abfd);
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  struct elf_link_hash_table *htab = elf_hash_table (info);
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  if (htab->irelifunc != NULL || htab->iplt != NULL)
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    return TRUE;
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  flags = bed->dynamic_sec_flags;
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  pltflags = flags;
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  if (bed->plt_not_loaded)
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    /* We do not clear SEC_ALLOC here because we still want the OS to
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       allocate space for the section; it's just that there's nothing
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       to read in from the object file.  */
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    pltflags &= ~ (SEC_CODE | SEC_LOAD | SEC_HAS_CONTENTS);
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  else
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    pltflags |= SEC_ALLOC | SEC_CODE | SEC_LOAD;
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  if (bed->plt_readonly)
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    pltflags |= SEC_READONLY;
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  if (info->shared)
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    {
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      /* We need to create .rel[a].ifunc for shared objects.  */
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      const char *rel_sec = (bed->rela_plts_and_copies_p
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                             ? ".rela.ifunc" : ".rel.ifunc");
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      s = bfd_make_section_with_flags (abfd, rel_sec,
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                                       flags | SEC_READONLY);
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      if (s == NULL
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          || ! bfd_set_section_alignment (abfd, s,
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                                          bed->s->log_file_align))
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        return FALSE;
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      htab->irelifunc = s;
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    }
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  else
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    {
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      /* We need to create .iplt, .rel[a].iplt, .igot and .igot.plt
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         for static executables.   */
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      s = bfd_make_section_with_flags (abfd, ".iplt", pltflags);
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      if (s == NULL
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          || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
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        return FALSE;
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      htab->iplt = s;
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      s = bfd_make_section_with_flags (abfd,
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                                       (bed->rela_plts_and_copies_p
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                                        ? ".rela.iplt" : ".rel.iplt"),
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                                       flags | SEC_READONLY);
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      if (s == NULL
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          || ! bfd_set_section_alignment (abfd, s,
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                                          bed->s->log_file_align))
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        return FALSE;
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      htab->irelplt = s;
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      /* We don't need the .igot section if we have the .igot.plt
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         section.  */
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      if (bed->want_got_plt)
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        s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
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      else
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        s = bfd_make_section_with_flags (abfd, ".igot", flags);
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      if (s == NULL
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          || !bfd_set_section_alignment (abfd, s,
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                                         bed->s->log_file_align))
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        return FALSE;
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      htab->igotplt = s;
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    }
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  return TRUE;
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}
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/* For a STT_GNU_IFUNC symbol, create a dynamic reloc section, SRELOC,
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   for the input section, SEC, and append this reloc to HEAD.  */
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asection *
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_bfd_elf_create_ifunc_dyn_reloc (bfd *abfd, struct bfd_link_info *info,
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                                 asection *sec, asection *sreloc,
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                                 struct elf_dyn_relocs **head)
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{
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  struct elf_dyn_relocs *p;
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  struct elf_link_hash_table *htab = elf_hash_table (info);
117
 
118
  if (sreloc == NULL)
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    {
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      const struct elf_backend_data *bed = get_elf_backend_data (abfd);
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      if (htab->dynobj == NULL)
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        htab->dynobj = abfd;
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      sreloc = _bfd_elf_make_dynamic_reloc_section (sec, htab->dynobj,
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                                                    bed->s->log_file_align,
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                                                    abfd,
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                                                    bed->rela_plts_and_copies_p);
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      if (sreloc == NULL)
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        return NULL;
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    }
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  p = *head;
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  if (p == NULL || p->sec != sec)
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    {
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      bfd_size_type amt = sizeof *p;
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      p = ((struct elf_dyn_relocs *) bfd_alloc (htab->dynobj, amt));
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      if (p == NULL)
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        return NULL;
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      p->next = *head;
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      *head = p;
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      p->sec = sec;
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      p->count = 0;
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      p->pc_count = 0;
146
    }
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  p->count += 1;
148
 
149
  return sreloc;
150
}
151
 
152
/* Allocate space in .plt, .got and associated reloc sections for
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   dynamic relocs against a STT_GNU_IFUNC symbol definition.  */
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bfd_boolean
156
_bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
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                                    struct elf_link_hash_entry *h,
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                                    struct elf_dyn_relocs **head,
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                                    unsigned int plt_entry_size,
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                                    unsigned int got_entry_size)
161
{
162
  asection *plt, *gotplt, *relplt;
163
  struct elf_dyn_relocs *p;
164
  unsigned int sizeof_reloc;
165
  const struct elf_backend_data *bed;
166
  struct elf_link_hash_table *htab;
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168
  /* When a shared library references a STT_GNU_IFUNC symbol defined
169
     in executable, the address of the resolved function may be used.
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     But in non-shared executable, the address of its .plt slot may
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     be used.  Pointer equality may not work correctly.  PIE should
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     be used if pointer equality is required here.  */
173
  if (!info->shared
174
      && (h->dynindx != -1
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          || info->export_dynamic)
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      && h->pointer_equality_needed)
177
    {
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      info->callbacks->einfo
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        (_("%F%P: dynamic STT_GNU_IFUNC symbol `%s' with pointer "
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           "equality in `%B' can not be used when making an "
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           "executable; recompile with -fPIE and relink with -pie\n"),
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         h->root.root.string,
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         h->root.u.def.section->owner);
184
      bfd_set_error (bfd_error_bad_value);
185
      return FALSE;
186
    }
187
 
188
  htab = elf_hash_table (info);
189
 
190
  /* Return and discard space for dynamic relocations against it if
191
     it is never referenced in a non-shared object.  */
192
  if (!h->ref_regular)
193
    {
194
      if (h->plt.refcount > 0
195
          || h->got.refcount > 0)
196
        abort ();
197
      h->got = htab->init_got_offset;
198
      h->plt = htab->init_plt_offset;
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      *head = NULL;
200
      return TRUE;
201
    }
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  bed = get_elf_backend_data (info->output_bfd);
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  if (bed->rela_plts_and_copies_p)
205
    sizeof_reloc = bed->s->sizeof_rela;
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  else
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    sizeof_reloc = bed->s->sizeof_rel;
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209
  /* When building a static executable, use .iplt, .igot.plt and
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     .rel[a].iplt sections for STT_GNU_IFUNC symbols.  */
211
  if (htab->splt != NULL)
212
    {
213
      plt = htab->splt;
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      gotplt = htab->sgotplt;
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      relplt = htab->srelplt;
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217
      /* If this is the first .plt entry, make room for the special
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         first entry.  */
219
      if (plt->size == 0)
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        plt->size += plt_entry_size;
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    }
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  else
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    {
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      plt = htab->iplt;
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      gotplt = htab->igotplt;
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      relplt = htab->irelplt;
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    }
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229
  /* Don't update value of STT_GNU_IFUNC symbol to PLT.  We need
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     the original value for R_*_IRELATIVE.  */
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  h->plt.offset = plt->size;
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233
  /* Make room for this entry in the .plt/.iplt section.  */
234
  plt->size += plt_entry_size;
235
 
236
  /* We also need to make an entry in the .got.plt/.got.iplt section,
237
     which will be placed in the .got section by the linker script.  */
238
  gotplt->size += got_entry_size;
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240
  /* We also need to make an entry in the .rel[a].plt/.rel[a].iplt
241
     section.  */
242
  relplt->size += sizeof_reloc;
243
  relplt->reloc_count++;
244
 
245
  /* We need dynamic relocation for STT_GNU_IFUNC symbol only when
246
     there is a non-GOT reference in a shared object.  */
247
  if (!info->shared
248
      || !h->non_got_ref)
249
    *head = NULL;
250
 
251
  /* Finally, allocate space.  */
252
  for (p = *head; p != NULL; p = p->next)
253
    htab->irelifunc->size += p->count * sizeof_reloc;
254
 
255
  /* For STT_GNU_IFUNC symbol, .got.plt has the real function addres
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     and .got has the PLT entry adddress.  We will load the GOT entry
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     with the PLT entry in finish_dynamic_symbol if it is used.  For
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     branch, it uses .got.plt.  For symbol value,
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     1. Use .got.plt in a shared object if it is forced local or not
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     dynamic.
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     2. Use .got.plt in a non-shared object if pointer equality isn't
262
     needed.
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     3. Use .got.plt in PIE.
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     4. Use .got.plt if .got isn't used.
265
     5. Otherwise use .got so that it can be shared among different
266
     objects at run-time.
267
     We only need to relocate .got entry in shared object.  */
268
  if ((info->shared
269
       && (h->dynindx == -1
270
           || h->forced_local))
271
      || (!info->shared
272
          && !h->pointer_equality_needed)
273
      || (info->executable && info->shared)
274
      || htab->sgot == NULL)
275
    {
276
      /* Use .got.plt.  */
277
      h->got.offset = (bfd_vma) -1;
278
    }
279
  else
280
    {
281
      h->got.offset = htab->sgot->size;
282
      htab->sgot->size += got_entry_size;
283
      if (info->shared)
284
        htab->srelgot->size += sizeof_reloc;
285
    }
286
 
287
  return TRUE;
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}

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