bfd/elf-s390-common.c

   1 /* IBM S/390-specific support for ELF 32 and 64 bit functions
   2    Copyright (C) 2000-2017 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 (bfd_link_pic (info))
  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 {
  92   struct elf_dyn_relocs *p;
  93   struct elf_link_hash_table *htab;
  94   struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
  95   struct elf_dyn_relocs **head = &eh->dyn_relocs;
  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 (bfd_link_pic (info)
 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 (bfd_link_pde (info)
 155       && h->def_regular
 156       && h->ref_dynamic)
 157     {
 158       h->root.u.def.section = htab->iplt;
 159       h->root.u.def.value = h->plt.offset;
 160       h->size = PLT_ENTRY_SIZE;
 161       h->type = STT_FUNC;
 162     }
 163
 164   /* We need dynamic relocation for STT_GNU_IFUNC symbol only when
 165      there is a non-GOT reference in a shared object.  */
 166   if (!bfd_link_pic (info) || !h->non_got_ref)
 167     *head = NULL;
 168
 169   /* Finally, allocate space.  */
 170   p = *head;
 171   if (p != NULL)
 172     {
 173       bfd_size_type count = 0;
 174       do
 175         {
 176           count += p->count;
 177           p = p->next;
 178         }
 179       while (p != NULL);
 180       htab->irelifunc->size += count * RELA_ENTRY_SIZE;
 181     }
 182
 183   /* Decide whether the got.iplt slot can be used.  This has to be
 184      avoided if the values in the GOT slots could differ for pointer
 185      equality reasons.  */
 186   if (h->got.refcount <= 0
 187       || (bfd_link_pic (info)
 188           && (h->dynindx == -1 || h->forced_local))
 189       || bfd_link_pie (info)
 190       || htab->sgot == NULL)
 191     {
 192       /* Use .got.iplt.  */
 193       h->got.offset = (bfd_vma) -1;
 194     }
 195   else
 196     {
 197       h->got.offset = htab->sgot->size;
 198       htab->sgot->size += GOT_ENTRY_SIZE;
 199       if (bfd_link_pic (info))
 200         htab->srelgot->size += RELA_ENTRY_SIZE;
 201     }
 202
 203   return TRUE;
 204 }
 205
 206 static bfd_boolean
 207 elf_s390_allocate_local_syminfo (bfd *abfd, Elf_Internal_Shdr *symtab_hdr)
 208 {
 209   bfd_size_type size;
 210
 211   size = symtab_hdr->sh_info;
 212   size *= (sizeof (bfd_signed_vma)       /* local got */
 213            + sizeof (struct plt_entry)   /* local plt */
 214            + sizeof(char));              /* local tls type */
 215   elf_local_got_refcounts (abfd) = ((bfd_signed_vma *)
 216                                     bfd_zalloc (abfd, size));
 217   if (elf_local_got_refcounts (abfd) == NULL)
 218     return FALSE;
 219   elf_s390_local_plt (abfd)
 220     = (struct plt_entry*)(elf_local_got_refcounts (abfd)
 221                           + symtab_hdr->sh_info);
 222   elf_s390_local_got_tls_type (abfd)
 223     = (char *) (elf_s390_local_plt (abfd) + symtab_hdr->sh_info);
 224
 225   return TRUE;
 226 }
 227
 228 /* Pick ELFOSABI_GNU if IFUNC symbols are used.  */
 229
 230 static bfd_boolean
 231 elf_s390_add_symbol_hook (bfd *abfd,
 232                           struct bfd_link_info *info,
 233                           Elf_Internal_Sym *sym,
 234                           const char **namep ATTRIBUTE_UNUSED,
 235                           flagword *flagsp ATTRIBUTE_UNUSED,
 236                           asection **secp ATTRIBUTE_UNUSED,
 237                           bfd_vma *valp ATTRIBUTE_UNUSED)
 238 {
 239   if (ELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC
 240       && (abfd->flags & DYNAMIC) == 0
 241       && bfd_get_flavour (info->output_bfd) == bfd_target_elf_flavour)
 242     elf_tdata (info->output_bfd)->has_gnu_symbols |= elf_gnu_symbol_ifunc;
 243
 244   return TRUE;
 245 }
 246
 247 /* Whether to sort relocs output by ld -r or ld --emit-relocs, by
 248    r_offset.  Don't do so for code sections.  We want to keep ordering
 249    of GDCALL / PLT32DBL for TLS optimizations as is.  On the other
 250    hand, elf-eh-frame.c processing requires .eh_frame relocs to be
 251    sorted.  */
 252
 253 static bfd_boolean
 254 elf_s390_elf_sort_relocs_p (asection *sec)
 255 {
 256   return (sec->flags & SEC_CODE) == 0;
 257 }
 258
 259 /* Merge object attributes from IBFD into OBFD.  Raise an error if
 260    there are conflicting attributes.  */
 261 static bfd_boolean
 262 elf_s390_merge_obj_attributes (bfd *ibfd, struct bfd_link_info *info)
 263 {
 264   bfd *obfd = info->output_bfd;
 265   obj_attribute *in_attr, *in_attrs;
 266   obj_attribute *out_attr, *out_attrs;
 267
 268   if (!elf_known_obj_attributes_proc (obfd)[0].i)
 269     {
 270       /* This is the first object.  Copy the attributes.  */
 271       _bfd_elf_copy_obj_attributes (ibfd, obfd);
 272
 273       /* Use the Tag_null value to indicate the attributes have been
 274          initialized.  */
 275       elf_known_obj_attributes_proc (obfd)[0].i = 1;
 276
 277       return TRUE;
 278     }
 279
 280   in_attrs = elf_known_obj_attributes (ibfd)[OBJ_ATTR_GNU];
 281   out_attrs = elf_known_obj_attributes (obfd)[OBJ_ATTR_GNU];
 282
 283   /* Check for conflicting Tag_GNU_S390_ABI_Vector attributes and
 284      merge non-conflicting ones.  */
 285   in_attr = &in_attrs[Tag_GNU_S390_ABI_Vector];
 286   out_attr = &out_attrs[Tag_GNU_S390_ABI_Vector];
 287
 288   if (in_attr->i > 2)
 289     _bfd_error_handler
 290       /* xgettext:c-format */
 291       (_("Warning: %B uses unknown vector ABI %d"), ibfd,
 292        in_attr->i);
 293   else if (out_attr->i > 2)
 294     _bfd_error_handler
 295       /* xgettext:c-format */
 296       (_("Warning: %B uses unknown vector ABI %d"), obfd,
 297        out_attr->i);
 298   else if (in_attr->i != out_attr->i)
 299     {
 300       out_attr->type = ATTR_TYPE_FLAG_INT_VAL;
 301
 302       if (in_attr->i && out_attr->i)
 303         {
 304           const char abi_str[3][9] = { "none", "software", "hardware" };
 305
 306           _bfd_error_handler
 307             /* xgettext:c-format */
 308             (_("Warning: %B uses vector %s ABI, %B uses %s ABI"),
 309              ibfd, obfd, abi_str[in_attr->i], abi_str[out_attr->i]);
 310         }
 311       if (in_attr->i > out_attr->i)
 312         out_attr->i = in_attr->i;
 313     }
 314
 315   /* Merge Tag_compatibility attributes and any common GNU ones.  */
 316   _bfd_elf_merge_object_attributes (ibfd, info);
 317
 318   return TRUE;
 319 }