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
  29 /* Return true if symbol NAME, as defined by ABFD, is one of the special
  30    __GOTT_BASE__ or __GOTT_INDEX__ symbols.  */
  31
  32 static bfd_boolean
  33 elf_vxworks_gott_symbol_p (bfd *abfd, const char *name)
  34 {
  35   char leading;
  36
  37   leading = bfd_get_symbol_leading_char (abfd);
  38   if (leading)
  39     {
  40       if (*name != leading)
  41         return FALSE;
  42       name++;
  43     }
  44   return (strcmp (name, "__GOTT_BASE__") == 0
  45           || strcmp (name, "__GOTT_INDEX__") == 0);
  46 }
  47
  48 /* Tweak magic VxWorks symbols as they are loaded.  */
  49 bfd_boolean
  50 elf_vxworks_add_symbol_hook (bfd *abfd,
  51                              struct bfd_link_info *info,
  52                              Elf_Internal_Sym *sym,
  53                              const char **namep,
  54                              flagword *flagsp,
  55                              asection **secp ATTRIBUTE_UNUSED,
  56                              bfd_vma *valp ATTRIBUTE_UNUSED)
  57 {
  58   /* Ideally these "magic" symbols would be exported by libc.so.1
  59      which would be found via a DT_NEEDED tag, and then handled
  60      specially by the linker at runtime.  Except shared libraries
  61      don't even link to libc.so.1 by default...
  62      If the symbol is imported from, or will be put in a shared library,
  63      give the symbol weak binding to get the desired samantics.
  64      This transformation will be undone in
  65      elf_i386_vxworks_link_output_symbol_hook. */
  66   if ((info->shared || abfd->flags & DYNAMIC)
  67       && elf_vxworks_gott_symbol_p (abfd, *namep))
  68     {
  69       sym->st_info = ELF_ST_INFO (STB_WEAK, ELF_ST_TYPE (sym->st_info));
  70       *flagsp |= BSF_WEAK;
  71     }
  72
  73   return TRUE;
  74 }
  75
  76 /* Perform VxWorks-specific handling of the create_dynamic_sections hook.
  77    When creating an executable, set *SRELPLT2_OUT to the .rel(a).plt.unloaded
  78    section.  */
  79
  80 bfd_boolean
  81 elf_vxworks_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info,
  82                                      asection **srelplt2_out)
  83 {
  84   struct elf_link_hash_table *htab;
  85   const struct elf_backend_data *bed;
  86   asection *s;
  87
  88   htab = elf_hash_table (info);
  89   bed = get_elf_backend_data (dynobj);
  90
  91   if (!info->shared)
  92     {
  93       s = bfd_make_section_with_flags (dynobj,
  94                                        bed->default_use_rela_p
  95                                        ? ".rela.plt.unloaded"
  96                                        : ".rel.plt.unloaded",
  97                                        SEC_HAS_CONTENTS | SEC_IN_MEMORY
  98                                        | SEC_READONLY | SEC_LINKER_CREATED);
  99       if (s == NULL
 100           || !bfd_set_section_alignment (dynobj, s, bed->s->log_file_align))
 101         return FALSE;
 102
 103       *srelplt2_out = s;
 104     }
 105
 106   /* Mark the GOT and PLT symbols as having relocations; they might
 107      not, but we won't know for sure until we build the GOT in
 108      finish_dynamic_symbol.  Also make sure that the GOT symbol
 109      is entered into the dynamic symbol table; the loader uses it
 110      to initialize __GOTT_BASE__[__GOTT_INDEX__].  */
 111   if (htab->hgot)
 112     {
 113       htab->hgot->indx = -2;
 114       htab->hgot->other &= ~ELF_ST_VISIBILITY (-1);
 115       htab->hgot->forced_local = 0;
 116       if (!bfd_elf_link_record_dynamic_symbol (info, htab->hgot))
 117         return FALSE;
 118     }
 119   if (htab->hplt)
 120     {
 121       htab->hplt->indx = -2;
 122       htab->hplt->type = STT_FUNC;
 123     }
 124
 125   return TRUE;
 126 }
 127
 128 /* Tweak magic VxWorks symbols as they are written to the output file.  */
 129 bfd_boolean
 130 elf_vxworks_link_output_symbol_hook (struct bfd_link_info *info
 131                                        ATTRIBUTE_UNUSED,
 132                                      const char *name,
 133                                      Elf_Internal_Sym *sym,
 134                                      asection *input_sec ATTRIBUTE_UNUSED,
 135                                      struct elf_link_hash_entry *h)
 136 {
 137   /* Reverse the effects of the hack in elf_vxworks_add_symbol_hook.  */
 138   if (h
 139       && h->root.type == bfd_link_hash_undefweak
 140       && elf_vxworks_gott_symbol_p (h->root.u.undef.abfd, name))
 141     sym->st_info = ELF_ST_INFO (STB_GLOBAL, ELF_ST_TYPE (sym->st_info));
 142
 143   return TRUE;
 144 }
 145
 146
 147 /* Copy relocations into the output file.  Fixes up relocations againt 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   Elf_Internal_Rela *irela;
 159   Elf_Internal_Rela *irelaend;
 160   int j;
 161
 162   bed = get_elf_backend_data (output_bfd);
 163
 164   irela = internal_relocs;
 165   irelaend = irela + (NUM_SHDR_ENTRIES (input_rel_hdr)
 166                       * bed->s->int_rels_per_ext_rel);
 167   while (irela < irelaend)
 168     {
 169       if ((output_bfd->flags & (DYNAMIC|EXEC_P))
 170           && *rel_hash
 171           && (*rel_hash)->def_dynamic
 172           && !(*rel_hash)->def_regular
 173           && ((*rel_hash)->root.type == bfd_link_hash_defined
 174               || (*rel_hash)->root.type == bfd_link_hash_defweak)
 175           && (*rel_hash)->root.u.def.section->output_section != NULL)
 176         {
 177           /* This is a relocation from an executable or shared library
 178              against a symbol in a different shared library.  We are
 179              creating a definition in the output file but it does not come
 180              from any of our normal (.o) files. ie. a PLT stub.
 181              Normally this would be a relocation against against SHN_UNDEF
 182              with the VMA of the PLT stub.  This upsets the VxWorks loader.
 183              Convert it to a section-relative relocation.
 184              This gets some other symbols (for instance .dynbss),
 185              but is conservatively correct.  */
 186           for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
 187             {
 188               asection *sec = (*rel_hash)->root.u.def.section;
 189               int this_idx = sec->output_section->target_index;
 190
 191               irela[j].r_info = ELF32_R_INFO (this_idx,
 192                   ELF32_R_TYPE (irela[j].r_info));
 193               irela[j].r_addend += (*rel_hash)->root.u.def.value;
 194               irela[j].r_addend += sec->output_offset;
 195             }
 196           /* Stop the generic routine adjusting this entry.  */
 197           *rel_hash = NULL;
 198         }
 199       irela += bed->s->int_rels_per_ext_rel;
 200       rel_hash++;
 201     }
 202   return _bfd_elf_link_output_relocs (output_bfd, input_section,
 203                                       input_rel_hdr, internal_relocs,
 204                                       rel_hash);
 205 }
 206
 207
 208 /* Set the sh_link and sh_info fields on the static plt relocation secton.  */
 209
 210 void
 211 elf_vxworks_final_write_processing (bfd *abfd,
 212                                     bfd_boolean linker ATTRIBUTE_UNUSED)
 213 {
 214   asection * sec;
 215   struct bfd_elf_section_data *d;
 216
 217   sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
 218   if (!sec)
 219     sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
 220   if (!sec)
 221     return;
 222   d = elf_section_data (sec);
 223   d->this_hdr.sh_link = elf_tdata (abfd)->symtab_section;
 224   sec = bfd_get_section_by_name (abfd, ".plt");
 225   if (sec)
 226     d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
 227 }