bfd/elf-s390-common.c

   1 /* IBM S/390-specific support for ELF 32 and 64 bit functions
   2    Copyright (C) 2000-2015 Free Software Foundation, Inc.
   3    Contributed by Andreas Krebbel.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
  20    02110-1301, USA.  */
  21
  22
  23 /* Return TRUE if H is an IFUNC symbol.  Simply checking for the
  24    symbol type might not be enough since it might get changed to
  25    STT_FUNC for pointer equality reasons.  */
  26 static inline bfd_boolean
  27 s390_is_ifunc_symbol_p (struct elf_link_hash_entry *h)
  28 {
  29   struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
  30   return h->type == STT_GNU_IFUNC || eh->ifunc_resolver_address != 0;
  31 }
  32
  33 /* Create sections needed by STT_GNU_IFUNC symbol.  */
  34
  35 static bfd_boolean
  36 s390_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
  37 {
  38   flagword flags;
  39   asection *s;
  40   const struct elf_backend_data *bed = get_elf_backend_data (abfd);
  41   struct elf_link_hash_table *htab = elf_hash_table (info);
  42
  43   if (htab->iplt != NULL)
  44     return TRUE;
  45
  46   flags = bed->dynamic_sec_flags;
  47
  48   if (info->shared)
  49     {
  50       s = bfd_make_section_with_flags (abfd, ".rela.ifunc",
  51                                        flags | SEC_READONLY);
  52       if (s == NULL
  53           || ! bfd_set_section_alignment (abfd, s,
  54                                           bed->s->log_file_align))
  55         return FALSE;
  56       htab->irelifunc = s;
  57     }
  58
  59   /* Create .iplt, .rel[a].iplt, and .igot.plt.  */
  60   s = bfd_make_section_with_flags (abfd, ".iplt",
  61                                    flags | SEC_CODE | SEC_READONLY);
  62   if (s == NULL
  63       || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
  64     return FALSE;
  65   htab->iplt = s;
  66
  67   s = bfd_make_section_with_flags (abfd, ".rela.iplt", flags | SEC_READONLY);
  68   if (s == NULL
  69       || ! bfd_set_section_alignment (abfd, s,
  70                                       bed->s->log_file_align))
  71     return FALSE;
  72   htab->irelplt = s;
  73
  74   s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
  75   if (s == NULL
  76       || !bfd_set_section_alignment (abfd, s,
  77                                      bed->s->log_file_align))
  78     return FALSE;
  79   htab->igotplt = s;
  80
  81   return TRUE;
  82 }
  83
  84
  85 /* Allocate space in .plt, .got and associated reloc sections for
  86    dynamic relocs against a STT_GNU_IFUNC symbol definition.  */
  87
  88 static bfd_boolean
  89 s390_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
  90                                     struct elf_link_hash_entry *h,
  91                                     struct elf_dyn_relocs **head)
  92 {
  93   struct elf_dyn_relocs *p;
  94   struct elf_link_hash_table *htab;
  95   struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
  96
  97   htab = elf_hash_table (info);
  98   eh->ifunc_resolver_address = h->root.u.def.value;
  99   eh->ifunc_resolver_section = h->root.u.def.section;
 100
 101   /* Support garbage collection against STT_GNU_IFUNC symbols.  */
 102   if (h->plt.refcount <= 0 && h->got.refcount <= 0)
 103     {
 104       /* When building shared library, we need to handle the case
 105          where it is marked with regular reference, but not non-GOT
 106          reference.  It may happen if we didn't see STT_GNU_IFUNC
 107          symbol at the time when checking relocations.  */
 108       if (info->shared
 109           && !h->non_got_ref
 110           && h->ref_regular)
 111         for (p = *head; p != NULL; p = p->next)
 112           if (p->count)
 113             {
 114               h->non_got_ref = 1;
 115               goto keep;
 116             }
 117
 118       h->got = htab->init_got_offset;
 119       h->plt = htab->init_plt_offset;
 120       *head = NULL;
 121       return TRUE;
 122     }
 123
 124   /* Return and discard space for dynamic relocations against it if
 125      it is never referenced in a non-shared object.  */
 126   if (!h->ref_regular)
 127     {
 128       if (h->plt.refcount > 0
 129           || h->got.refcount > 0)
 130         abort ();
 131       h->got = htab->init_got_offset;
 132       h->plt = htab->init_plt_offset;
 133       *head = NULL;
 134       return TRUE;
 135     }
 136
 137 keep:
 138   /* Without checking h->plt.refcount here we allocate a PLT slot.
 139      When setting plt.refcount in check_relocs it might not have been
 140      known that this will be an IFUNC symol.  */
 141   h->plt.offset = htab->iplt->size;
 142   h->needs_plt = 1;
 143   htab->iplt->size += PLT_ENTRY_SIZE;
 144   htab->igotplt->size += GOT_ENTRY_SIZE;
 145   htab->irelplt->size += RELA_ENTRY_SIZE;
 146   htab->irelplt->reloc_count++;
 147
 148   /* In order to make pointer equality work with IFUNC symbols defined
 149      in a non-PIE executable and referenced in a shared lib, we turn
 150      the symbol into a STT_FUNC symbol and make the symbol value to
 151      point to the IPLT slot.  That way the referencing shared lib will
 152      always get the PLT slot address when resolving the respective
 153      R_390_GLOB_DAT/R_390_64 relocs on that symbol.  */
 154   if (info->executable && !info->shared && h->def_regular && h->ref_dynamic)
 155     {
 156       h->root.u.def.section = htab->iplt;
 157       h->root.u.def.value = h->plt.offset;
 158       h->size = PLT_ENTRY_SIZE;
 159       h->type = STT_FUNC;
 160     }
 161
 162   /* We need dynamic relocation for STT_GNU_IFUNC symbol only when
 163      there is a non-GOT reference in a shared object.  */
 164   if (!info->shared || !h->non_got_ref)
 165     *head = NULL;
 166
 167   /* Finally, allocate space.  */
 168   p = *head;
 169   if (p != NULL)
 170     {
 171       bfd_size_type count = 0;
 172       do
 173         {
 174           count += p->count;
 175           p = p->next;
 176         }
 177       while (p != NULL);
 178       htab->irelifunc->size += count * RELA_ENTRY_SIZE;
 179     }
 180
 181   /* Decide whether the got.iplt slot can be used.  This has to be
 182      avoided if the values in the GOT slots could differ for pointer
 183      equality reasons.  */
 184   if (h->got.refcount <= 0
 185       || (info->shared
 186           && (h->dynindx == -1 || h->forced_local))
 187       || (info->executable && info->shared)
 188       || htab->sgot == NULL)
 189     {
 190       /* Use .got.iplt.  */
 191       h->got.offset = (bfd_vma) -1;
 192     }
 193   else
 194     {
 195       h->got.offset = htab->sgot->size;
 196       htab->sgot->size += GOT_ENTRY_SIZE;
 197       if (info->shared)
 198         htab->srelgot->size += RELA_ENTRY_SIZE;
 199     }
 200
 201   return TRUE;
 202 }
 203
 204 static bfd_boolean
 205 elf_s390_allocate_local_syminfo (bfd *abfd, Elf_Internal_Shdr *symtab_hdr)
 206 {
 207   bfd_size_type size;
 208
 209   size = symtab_hdr->sh_info;
 210   size *= (sizeof (bfd_signed_vma)       /* local got */
 211            + sizeof (struct plt_entry)   /* local plt */
 212            + sizeof(char));              /* local tls type */
 213   elf_local_got_refcounts (abfd) = ((bfd_signed_vma *)
 214                                     bfd_zalloc (abfd, size));
 215   if (elf_local_got_refcounts (abfd) == NULL)
 216     return FALSE;
 217   elf_s390_local_plt (abfd)
 218     = (struct plt_entry*)(elf_local_got_refcounts (abfd)
 219                           + symtab_hdr->sh_info);
 220   elf_s390_local_got_tls_type (abfd)
 221     = (char *) (elf_s390_local_plt (abfd) + symtab_hdr->sh_info);
 222
 223   return TRUE;
 224 }
 225
 226 /* Pick ELFOSABI_GNU if IFUNC symbols are used.  */
 227
 228 static bfd_boolean
 229 elf_s390_add_symbol_hook (bfd *abfd,
 230                           struct bfd_link_info *info,
 231                           Elf_Internal_Sym *sym,
 232                           const char **namep ATTRIBUTE_UNUSED,
 233                           flagword *flagsp ATTRIBUTE_UNUSED,
 234                           asection **secp ATTRIBUTE_UNUSED,
 235                           bfd_vma *valp ATTRIBUTE_UNUSED)
 236 {
 237   if ((ELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC
 238        || ELF_ST_BIND (sym->st_info) == STB_GNU_UNIQUE)
 239       && (abfd->flags & DYNAMIC) == 0
 240       && bfd_get_flavour (info->output_bfd) == bfd_target_elf_flavour)
 241     elf_tdata (info->output_bfd)->has_gnu_symbols = TRUE;
 242
 243   return TRUE;
 244 }
 245
 246 /* Whether to sort relocs output by ld -r or ld --emit-relocs, by
 247    r_offset.  Don't do so for code sections.  We want to keep ordering
 248    of GDCALL / PLT32DBL for TLS optimizations as is.  On the other
 249    hand, elf-eh-frame.c processing requires .eh_frame relocs to be
 250    sorted.  */
 251
 252 static bfd_boolean
 253 elf_s390_elf_sort_relocs_p (asection *sec)
 254 {
 255   return (sec->flags & SEC_CODE) == 0;
 256 }