bfd/elf-vxworks.c

   1 /* VxWorks support for ELF
   2    Copyright 2005, 2007 Free Software Foundation, Inc.
   3
   4    This file is part of BFD, the Binary File Descriptor library.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  19    MA 02111-1307, USA.  */
  20
  21 /* This file provides routines used by all VxWorks targets.  */
  22
  23 #include "sysdep.h"
  24 #include "bfd.h"
  25 #include "libbfd.h"
  26 #include "elf-bfd.h"
  27 #include "elf-vxworks.h"
  28 #include "elf/vxworks.h"
  29
  30 /* Return true if symbol NAME, as defined by ABFD, is one of the special
  31    __GOTT_BASE__ or __GOTT_INDEX__ symbols.  */
  32
  33 static bfd_boolean
  34 elf_vxworks_gott_symbol_p (bfd *abfd, const char *name)
  35 {
  36   char leading;
  37
  38   leading = bfd_get_symbol_leading_char (abfd);
  39   if (leading)
  40     {
  41       if (*name != leading)
  42         return FALSE;
  43       name++;
  44     }
  45   return (strcmp (name, "__GOTT_BASE__") == 0
  46           || strcmp (name, "__GOTT_INDEX__") == 0);
  47 }
  48
  49 /* Tweak magic VxWorks symbols as they are loaded.  */
  50 bfd_boolean
  51 elf_vxworks_add_symbol_hook (bfd *abfd,
  52                              struct bfd_link_info *info,
  53                              Elf_Internal_Sym *sym,
  54                              const char **namep,
  55                              flagword *flagsp,
  56                              asection **secp ATTRIBUTE_UNUSED,
  57                              bfd_vma *valp ATTRIBUTE_UNUSED)
  58 {
  59   /* Ideally these "magic" symbols would be exported by libc.so.1
  60      which would be found via a DT_NEEDED tag, and then handled
  61      specially by the linker at runtime.  Except shared libraries
  62      don't even link to libc.so.1 by default...
  63      If the symbol is imported from, or will be put in a shared library,
  64      give the symbol weak binding to get the desired samantics.
  65      This transformation will be undone in
  66      elf_i386_vxworks_link_output_symbol_hook. */
  67   if ((info->shared || abfd->flags & DYNAMIC)
  68       && elf_vxworks_gott_symbol_p (abfd, *namep))
  69     {
  70       sym->st_info = ELF_ST_INFO (STB_WEAK, ELF_ST_TYPE (sym->st_info));
  71       *flagsp |= BSF_WEAK;
  72     }
  73
  74   return TRUE;
  75 }
  76
  77 /* Perform VxWorks-specific handling of the create_dynamic_sections hook.
  78    When creating an executable, set *SRELPLT2_OUT to the .rel(a).plt.unloaded
  79    section.  */
  80
  81 bfd_boolean
  82 elf_vxworks_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info,
  83                                      asection **srelplt2_out)
  84 {
  85   struct elf_link_hash_table *htab;
  86   const struct elf_backend_data *bed;
  87   asection *s;
  88
  89   htab = elf_hash_table (info);
  90   bed = get_elf_backend_data (dynobj);
  91
  92   if (!info->shared)
  93     {
  94       s = bfd_make_section_with_flags (dynobj,
  95                                        bed->default_use_rela_p
  96                                        ? ".rela.plt.unloaded"
  97                                        : ".rel.plt.unloaded",
  98                                        SEC_HAS_CONTENTS | SEC_IN_MEMORY
  99                                        | SEC_READONLY | SEC_LINKER_CREATED);
 100       if (s == NULL
 101           || !bfd_set_section_alignment (dynobj, s, bed->s->log_file_align))
 102         return FALSE;
 103
 104       *srelplt2_out = s;
 105     }
 106
 107   /* Mark the GOT and PLT symbols as having relocations; they might
 108      not, but we won't know for sure until we build the GOT in
 109      finish_dynamic_symbol.  Also make sure that the GOT symbol
 110      is entered into the dynamic symbol table; the loader uses it
 111      to initialize __GOTT_BASE__[__GOTT_INDEX__].  */
 112   if (htab->hgot)
 113     {
 114       htab->hgot->indx = -2;
 115       htab->hgot->other &= ~ELF_ST_VISIBILITY (-1);
 116       htab->hgot->forced_local = 0;
 117       if (!bfd_elf_link_record_dynamic_symbol (info, htab->hgot))
 118         return FALSE;
 119     }
 120   if (htab->hplt)
 121     {
 122       htab->hplt->indx = -2;
 123       htab->hplt->type = STT_FUNC;
 124     }
 125
 126   return TRUE;
 127 }
 128
 129 /* Tweak magic VxWorks symbols as they are written to the output file.  */
 130 int
 131 elf_vxworks_link_output_symbol_hook (struct bfd_link_info *info
 132                                        ATTRIBUTE_UNUSED,
 133                                      const char *name,
 134                                      Elf_Internal_Sym *sym,
 135                                      asection *input_sec ATTRIBUTE_UNUSED,
 136                                      struct elf_link_hash_entry *h)
 137 {
 138   /* Reverse the effects of the hack in elf_vxworks_add_symbol_hook.  */
 139   if (h
 140       && h->root.type == bfd_link_hash_undefweak
 141       && elf_vxworks_gott_symbol_p (h->root.u.undef.abfd, name))
 142     sym->st_info = ELF_ST_INFO (STB_GLOBAL, ELF_ST_TYPE (sym->st_info));
 143
 144   return 1;
 145 }
 146
 147 /* Copy relocations into the output file.  Fixes up relocations against PLT
 148    entries, then calls the generic routine.  */
 149
 150 bfd_boolean
 151 elf_vxworks_emit_relocs (bfd *output_bfd,
 152                          asection *input_section,
 153                          Elf_Internal_Shdr *input_rel_hdr,
 154                          Elf_Internal_Rela *internal_relocs,
 155                          struct elf_link_hash_entry **rel_hash)
 156 {
 157   const struct elf_backend_data *bed;
 158   int j;
 159
 160   bed = get_elf_backend_data (output_bfd);
 161
 162   if (output_bfd->flags & (DYNAMIC|EXEC_P))
 163     {
 164       Elf_Internal_Rela *irela;
 165       Elf_Internal_Rela *irelaend;
 166       struct elf_link_hash_entry **hash_ptr;
 167
 168       for (irela = internal_relocs,
 169              irelaend = irela + (NUM_SHDR_ENTRIES (input_rel_hdr)
 170                                  * bed->s->int_rels_per_ext_rel),
 171              hash_ptr = rel_hash;
 172            irela < irelaend;
 173            irela += bed->s->int_rels_per_ext_rel,
 174              hash_ptr++)
 175         {
 176           if (*hash_ptr
 177               && (*hash_ptr)->def_dynamic
 178               && !(*hash_ptr)->def_regular
 179               && ((*hash_ptr)->root.type == bfd_link_hash_defined
 180                   || (*hash_ptr)->root.type == bfd_link_hash_defweak)
 181               && (*hash_ptr)->root.u.def.section->output_section != NULL)
 182             {
 183               /* This is a relocation from an executable or shared
 184                  library against a symbol in a different shared
 185                  library.  We are creating a definition in the output
 186                  file but it does not come from any of our normal (.o)
 187                  files. ie. a PLT stub.  Normally this would be a
 188                  relocation against against SHN_UNDEF with the VMA of
 189                  the PLT stub.  This upsets the VxWorks loader.
 190                  Convert it to a section-relative relocation.  This
 191                  gets some other symbols (for instance .dynbss), but
 192                  is conservatively correct.  */
 193               for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
 194                 {
 195                   asection *sec = (*hash_ptr)->root.u.def.section;
 196                   int this_idx = sec->output_section->target_index;
 197
 198                   irela[j].r_info
 199                     = ELF32_R_INFO (this_idx, ELF32_R_TYPE (irela[j].r_info));
 200                   irela[j].r_addend += (*hash_ptr)->root.u.def.value;
 201                   irela[j].r_addend += sec->output_offset;
 202                 }
 203               /* Stop the generic routine adjusting this entry.  */
 204               *hash_ptr = NULL;
 205             }
 206         }
 207     }
 208   return _bfd_elf_link_output_relocs (output_bfd, input_section,
 209                                       input_rel_hdr, internal_relocs,
 210                                       rel_hash);
 211 }
 212
 213
 214 /* Set the sh_link and sh_info fields on the static plt relocation secton.  */
 215
 216 void
 217 elf_vxworks_final_write_processing (bfd *abfd,
 218                                     bfd_boolean linker ATTRIBUTE_UNUSED)
 219 {
 220   asection * sec;
 221   struct bfd_elf_section_data *d;
 222
 223   sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
 224   if (!sec)
 225     sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
 226   if (!sec)
 227     return;
 228   d = elf_section_data (sec);
 229   d->this_hdr.sh_link = elf_tdata (abfd)->symtab_section;
 230   sec = bfd_get_section_by_name (abfd, ".plt");
 231   if (sec)
 232     d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
 233 }
 234
 235 /* Add the dynamic entries required by VxWorks.  These point to the
 236    tls sections.  */
 237
 238 bfd_boolean
 239 elf_vxworks_add_dynamic_entries (bfd *output_bfd, struct bfd_link_info *info)
 240 {
 241   if (bfd_get_section_by_name (output_bfd, ".tls_data"))
 242     {
 243       if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_START, 0)
 244           || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_SIZE, 0)
 245           || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_ALIGN, 0))
 246         return FALSE;
 247     }
 248   if (bfd_get_section_by_name (output_bfd, ".tls_vars"))
 249     {
 250       if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_START, 0)
 251           || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_SIZE, 0))
 252         return FALSE;
 253     }
 254   return TRUE;
 255 }
 256
 257 /* If *DYN is one of the VxWorks-specific dynamic entries, then fill
 258    in the value now  and return TRUE.  Otherwise return FALSE.  */
 259
 260 bfd_boolean
 261 elf_vxworks_finish_dynamic_entry (bfd *output_bfd, Elf_Internal_Dyn *dyn)
 262 {
 263   asection *sec;
 264
 265   switch (dyn->d_tag)
 266     {
 267     default:
 268       return FALSE;
 269
 270     case DT_VX_WRS_TLS_DATA_START:
 271       sec = bfd_get_section_by_name (output_bfd, ".tls_data");
 272       dyn->d_un.d_ptr = sec->vma;
 273       break;
 274
 275     case DT_VX_WRS_TLS_DATA_SIZE:
 276       sec = bfd_get_section_by_name (output_bfd, ".tls_data");
 277       dyn->d_un.d_val = sec->size;
 278       break;
 279
 280     case DT_VX_WRS_TLS_DATA_ALIGN:
 281       sec = bfd_get_section_by_name (output_bfd, ".tls_data");
 282       dyn->d_un.d_val
 283         = (bfd_size_type)1 << bfd_get_section_alignment (abfd, sec);
 284       break;
 285
 286     case DT_VX_WRS_TLS_VARS_START:
 287       sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
 288       dyn->d_un.d_ptr = sec->vma;
 289       break;
 290
 291     case DT_VX_WRS_TLS_VARS_SIZE:
 292       sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
 293       dyn->d_un.d_val = sec->size;
 294       break;
 295     }
 296   return TRUE;
 297 }
 298
 299