bfd/elf-s390-common.c

   1 /* IBM S/390-specific support for ELF 32 and 64 bit functions
   2    Copyright (C) 2000-2019 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 /* Return true if .got.plt is supposed to be emitted after .got.  */
  34
  35 static inline bfd_boolean
  36 s390_gotplt_after_got_p (struct bfd_link_info *info)
  37 {
  38   struct elf_s390_link_hash_table *htab = elf_s390_hash_table (info);
  39
  40   if (!htab->elf.sgot || !htab->elf.sgotplt)
  41     return TRUE;
  42
  43   if (htab->elf.sgot->output_section == htab->elf.sgotplt->output_section)
  44     {
  45       if (htab->elf.sgot->output_offset < htab->elf.sgotplt->output_offset)
  46         return TRUE;
  47     }
  48   else
  49     {
  50       if (htab->elf.sgot->output_section->vma
  51           <= htab->elf.sgotplt->output_section->vma)
  52         return TRUE;
  53     }
  54   return FALSE;
  55 }
  56
  57 /* Return the value of the _GLOBAL_OFFSET_TABLE_ symbol.  */
  58
  59 static inline bfd_vma
  60 s390_got_pointer (struct bfd_link_info *info)
  61 {
  62   struct elf_s390_link_hash_table *htab = elf_s390_hash_table (info);
  63   bfd_vma got_pointer;
  64
  65   BFD_ASSERT (htab && htab->elf.hgot);
  66
  67   got_pointer = (htab->elf.hgot->root.u.def.section->output_section->vma
  68                  + htab->elf.hgot->root.u.def.section->output_offset);
  69   /* Our ABI requires the GOT pointer to point at the very beginning
  70      of the global offset table.  */
  71   BFD_ASSERT (got_pointer
  72               <= (htab->elf.sgot->output_section->vma
  73                   + htab->elf.sgot->output_offset));
  74   BFD_ASSERT (got_pointer
  75               <= (htab->elf.sgotplt->output_section->vma
  76                   + htab->elf.sgotplt->output_offset));
  77
  78   return got_pointer;
  79 }
  80
  81
  82 /* Return the offset of the .got versus _GLOBAL_OFFSET_TABLE_.  */
  83
  84 static inline bfd_vma
  85 s390_got_offset (struct bfd_link_info *info)
  86 {
  87   struct elf_s390_link_hash_table *htab = elf_s390_hash_table (info);
  88
  89   /* The absolute address of the .got in the target image.  */
  90   bfd_vma got_address = (htab->elf.sgot->output_section->vma
  91                          + htab->elf.sgot->output_offset);
  92
  93   /* GOT offset must not be negative.  */
  94   BFD_ASSERT (s390_got_pointer (info) <= got_address);
  95   return got_address - s390_got_pointer (info);
  96 }
  97
  98 /* Return the offset of the .got.plt versus _GLOBAL_OFFSET_TABLE_.  */
  99
 100 static inline bfd_vma
 101 s390_gotplt_offset (struct bfd_link_info *info)
 102 {
 103   struct elf_s390_link_hash_table *htab = elf_s390_hash_table (info);
 104
 105   /* The absolute address of the .got.plt in the target image.  */
 106   bfd_vma gotplt_address = (htab->elf.sgotplt->output_section->vma
 107                             + htab->elf.sgotplt->output_offset);
 108
 109   /* GOT offset must not be negative.  */
 110   BFD_ASSERT (s390_got_pointer (info) <= gotplt_address);
 111   return gotplt_address - s390_got_pointer (info);
 112 }
 113
 114 /* Create sections needed by STT_GNU_IFUNC symbol.  */
 115
 116 static bfd_boolean
 117 s390_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
 118 {
 119   flagword flags;
 120   asection *s;
 121   const struct elf_backend_data *bed = get_elf_backend_data (abfd);
 122   struct elf_link_hash_table *htab = elf_hash_table (info);
 123
 124   if (htab->iplt != NULL)
 125     return TRUE;
 126
 127   flags = bed->dynamic_sec_flags;
 128
 129   if (bfd_link_pic (info))
 130     {
 131       s = bfd_make_section_with_flags (abfd, ".rela.ifunc",
 132                                        flags | SEC_READONLY);
 133       if (s == NULL
 134           || !bfd_set_section_alignment (s, bed->s->log_file_align))
 135         return FALSE;
 136       htab->irelifunc = s;
 137     }
 138
 139   /* Create .iplt, .rel[a].iplt, and .igot.plt.  */
 140   s = bfd_make_section_with_flags (abfd, ".iplt",
 141                                    flags | SEC_CODE | SEC_READONLY);
 142   if (s == NULL
 143       || !bfd_set_section_alignment (s, bed->plt_alignment))
 144     return FALSE;
 145   htab->iplt = s;
 146
 147   s = bfd_make_section_with_flags (abfd, ".rela.iplt", flags | SEC_READONLY);
 148   if (s == NULL
 149       || !bfd_set_section_alignment (s, bed->s->log_file_align))
 150     return FALSE;
 151   htab->irelplt = s;
 152
 153   s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
 154   if (s == NULL
 155       || !bfd_set_section_alignment (s, bed->s->log_file_align))
 156     return FALSE;
 157   htab->igotplt = s;
 158
 159   return TRUE;
 160 }
 161
 162
 163 /* Allocate space in .plt, .got and associated reloc sections for
 164    dynamic relocs against a STT_GNU_IFUNC symbol definition.  */
 165
 166 static bfd_boolean
 167 s390_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
 168                                     struct elf_link_hash_entry *h)
 169 {
 170   struct elf_dyn_relocs *p;
 171   struct elf_link_hash_table *htab;
 172   struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
 173   struct elf_dyn_relocs **head = &eh->dyn_relocs;
 174
 175   htab = elf_hash_table (info);
 176   eh->ifunc_resolver_address = h->root.u.def.value;
 177   eh->ifunc_resolver_section = h->root.u.def.section;
 178
 179   /* Support garbage collection against STT_GNU_IFUNC symbols.  */
 180   if (h->plt.refcount <= 0 && h->got.refcount <= 0)
 181     {
 182       /* When building shared library, we need to handle the case
 183          where it is marked with regular reference, but not non-GOT
 184          reference.  It may happen if we didn't see STT_GNU_IFUNC
 185          symbol at the time when checking relocations.  */
 186       if (bfd_link_pic (info)
 187           && !h->non_got_ref
 188           && h->ref_regular)
 189         for (p = *head; p != NULL; p = p->next)
 190           if (p->count)
 191             {
 192               h->non_got_ref = 1;
 193               goto keep;
 194             }
 195
 196       h->got = htab->init_got_offset;
 197       h->plt = htab->init_plt_offset;
 198       *head = NULL;
 199       return TRUE;
 200     }
 201
 202   /* Return and discard space for dynamic relocations against it if
 203      it is never referenced in a non-shared object.  */
 204   if (!h->ref_regular)
 205     {
 206       if (h->plt.refcount > 0
 207           || h->got.refcount > 0)
 208         abort ();
 209       h->got = htab->init_got_offset;
 210       h->plt = htab->init_plt_offset;
 211       *head = NULL;
 212       return TRUE;
 213     }
 214
 215 keep:
 216   /* Without checking h->plt.refcount here we allocate a PLT slot.
 217      When setting plt.refcount in check_relocs it might not have been
 218      known that this will be an IFUNC symol.  */
 219   h->plt.offset = htab->iplt->size;
 220   h->needs_plt = 1;
 221   htab->iplt->size += PLT_ENTRY_SIZE;
 222   htab->igotplt->size += GOT_ENTRY_SIZE;
 223   htab->irelplt->size += RELA_ENTRY_SIZE;
 224   htab->irelplt->reloc_count++;
 225
 226   /* In order to make pointer equality work with IFUNC symbols defined
 227      in a non-PIE executable and referenced in a shared lib, we turn
 228      the symbol into a STT_FUNC symbol and make the symbol value to
 229      point to the IPLT slot.  That way the referencing shared lib will
 230      always get the PLT slot address when resolving the respective
 231      R_390_GLOB_DAT/R_390_64 relocs on that symbol.  */
 232   if (bfd_link_pde (info)
 233       && h->def_regular
 234       && h->ref_dynamic)
 235     {
 236       h->root.u.def.section = htab->iplt;
 237       h->root.u.def.value = h->plt.offset;
 238       h->size = PLT_ENTRY_SIZE;
 239       h->type = STT_FUNC;
 240     }
 241
 242   if (!bfd_link_pic (info))
 243     *head = NULL;
 244
 245   /* Finally, allocate space.  */
 246   p = *head;
 247   if (p != NULL)
 248     {
 249       bfd_size_type count = 0;
 250       do
 251         {
 252           count += p->count;
 253           p = p->next;
 254         }
 255       while (p != NULL);
 256       htab->irelifunc->size += count * RELA_ENTRY_SIZE;
 257     }
 258
 259   /* Decide whether the got.iplt slot can be used.  This has to be
 260      avoided if the values in the GOT slots could differ for pointer
 261      equality reasons.  */
 262   if (h->got.refcount <= 0
 263       || (bfd_link_pic (info)
 264           && (h->dynindx == -1 || h->forced_local))
 265       || bfd_link_pie (info)
 266       || htab->sgot == NULL)
 267     {
 268       /* Use .got.iplt.  */
 269       h->got.offset = (bfd_vma) -1;
 270     }
 271   else
 272     {
 273       h->got.offset = htab->sgot->size;
 274       htab->sgot->size += GOT_ENTRY_SIZE;
 275       if (bfd_link_pic (info))
 276         htab->srelgot->size += RELA_ENTRY_SIZE;
 277     }
 278
 279   return TRUE;
 280 }
 281
 282 static bfd_boolean
 283 elf_s390_allocate_local_syminfo (bfd *abfd, Elf_Internal_Shdr *symtab_hdr)
 284 {
 285   bfd_size_type size;
 286
 287   size = symtab_hdr->sh_info;
 288   size *= (sizeof (bfd_signed_vma)       /* local got */
 289            + sizeof (struct plt_entry)   /* local plt */
 290            + sizeof(char));              /* local tls type */
 291   elf_local_got_refcounts (abfd) = ((bfd_signed_vma *)
 292                                     bfd_zalloc (abfd, size));
 293   if (elf_local_got_refcounts (abfd) == NULL)
 294     return FALSE;
 295   elf_s390_local_plt (abfd)
 296     = (struct plt_entry*)(elf_local_got_refcounts (abfd)
 297                           + symtab_hdr->sh_info);
 298   elf_s390_local_got_tls_type (abfd)
 299     = (char *) (elf_s390_local_plt (abfd) + symtab_hdr->sh_info);
 300
 301   return TRUE;
 302 }
 303
 304 /* Whether to sort relocs output by ld -r or ld --emit-relocs, by
 305    r_offset.  Don't do so for code sections.  We want to keep ordering
 306    of GDCALL / PLT32DBL for TLS optimizations as is.  On the other
 307    hand, elf-eh-frame.c processing requires .eh_frame relocs to be
 308    sorted.  */
 309
 310 static bfd_boolean
 311 elf_s390_elf_sort_relocs_p (asection *sec)
 312 {
 313   return (sec->flags & SEC_CODE) == 0;
 314 }
 315
 316 /* Merge object attributes from IBFD into OBFD.  Raise an error if
 317    there are conflicting attributes.  */
 318 static bfd_boolean
 319 elf_s390_merge_obj_attributes (bfd *ibfd, struct bfd_link_info *info)
 320 {
 321   bfd *obfd = info->output_bfd;
 322   obj_attribute *in_attr, *in_attrs;
 323   obj_attribute *out_attr, *out_attrs;
 324
 325   if (!elf_known_obj_attributes_proc (obfd)[0].i)
 326     {
 327       /* This is the first object.  Copy the attributes.  */
 328       _bfd_elf_copy_obj_attributes (ibfd, obfd);
 329
 330       /* Use the Tag_null value to indicate the attributes have been
 331          initialized.  */
 332       elf_known_obj_attributes_proc (obfd)[0].i = 1;
 333
 334       return TRUE;
 335     }
 336
 337   in_attrs = elf_known_obj_attributes (ibfd)[OBJ_ATTR_GNU];
 338   out_attrs = elf_known_obj_attributes (obfd)[OBJ_ATTR_GNU];
 339
 340   /* Check for conflicting Tag_GNU_S390_ABI_Vector attributes and
 341      merge non-conflicting ones.  */
 342   in_attr = &in_attrs[Tag_GNU_S390_ABI_Vector];
 343   out_attr = &out_attrs[Tag_GNU_S390_ABI_Vector];
 344
 345   if (in_attr->i > 2)
 346     _bfd_error_handler
 347       /* xgettext:c-format */
 348       (_("warning: %pB uses unknown vector ABI %d"), ibfd,
 349        in_attr->i);
 350   else if (out_attr->i > 2)
 351     _bfd_error_handler
 352       /* xgettext:c-format */
 353       (_("warning: %pB uses unknown vector ABI %d"), obfd,
 354        out_attr->i);
 355   else if (in_attr->i != out_attr->i)
 356     {
 357       out_attr->type = ATTR_TYPE_FLAG_INT_VAL;
 358
 359       if (in_attr->i && out_attr->i)
 360         {
 361           const char abi_str[3][9] = { "none", "software", "hardware" };
 362
 363           _bfd_error_handler
 364             /* xgettext:c-format */
 365             (_("warning: %pB uses vector %s ABI, %pB uses %s ABI"),
 366              ibfd, abi_str[in_attr->i], obfd, abi_str[out_attr->i]);
 367         }
 368       if (in_attr->i > out_attr->i)
 369         out_attr->i = in_attr->i;
 370     }
 371
 372   /* Merge Tag_compatibility attributes and any common GNU ones.  */
 373   _bfd_elf_merge_object_attributes (ibfd, info);
 374
 375   return TRUE;
 376 }