bfd/elf-vxworks.c

   1 /* VxWorks support for ELF
   2    Copyright (C) 2005-2024 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, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* This file provides routines used by all VxWorks targets.  */
  20
  21 #include "sysdep.h"
  22 #include "bfd.h"
  23 #include "libbfd.h"
  24 #include "elf-bfd.h"
  25 #include "elf-vxworks.h"
  26 #include "elf/vxworks.h"
  27
  28 /* Return true if symbol NAME, as defined by ABFD, is one of the special
  29    __GOTT_BASE__ or __GOTT_INDEX__ symbols.  */
  30
  31 static bool
  32 elf_vxworks_gott_symbol_p (bfd *abfd, const char *name)
  33 {
  34   char leading;
  35
  36   leading = bfd_get_symbol_leading_char (abfd);
  37   if (leading)
  38     {
  39       if (*name != leading)
  40         return false;
  41       name++;
  42     }
  43   return (strcmp (name, "__GOTT_BASE__") == 0
  44           || strcmp (name, "__GOTT_INDEX__") == 0);
  45 }
  46
  47 /* Tweak magic VxWorks symbols as they are loaded.  */
  48 bool
  49 elf_vxworks_add_symbol_hook (bfd *abfd,
  50                              struct bfd_link_info *info,
  51                              Elf_Internal_Sym *sym,
  52                              const char **namep,
  53                              flagword *flagsp,
  54                              asection **secp ATTRIBUTE_UNUSED,
  55                              bfd_vma *valp ATTRIBUTE_UNUSED)
  56 {
  57   /* Ideally these "magic" symbols would be exported by libc.so.1
  58      which would be found via a DT_NEEDED tag, and then handled
  59      specially by the linker at runtime.  Except shared libraries
  60      don't even link to libc.so.1 by default...
  61      If the symbol is imported from, or will be put in a shared library,
  62      give the symbol weak binding to get the desired samantics.
  63      This transformation will be undone in
  64      elf_i386_vxworks_link_output_symbol_hook. */
  65   if ((bfd_link_pic (info) || abfd->flags & DYNAMIC)
  66       && elf_vxworks_gott_symbol_p (abfd, *namep))
  67     {
  68       sym->st_info = ELF_ST_INFO (STB_WEAK, ELF_ST_TYPE (sym->st_info));
  69       *flagsp |= BSF_WEAK;
  70     }
  71
  72   return true;
  73 }
  74
  75 /* Perform VxWorks-specific handling of the create_dynamic_sections hook.
  76    When creating an executable, set *SRELPLT2_OUT to the .rel(a).plt.unloaded
  77    section.  */
  78
  79 bool
  80 elf_vxworks_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info,
  81                                      asection **srelplt2_out)
  82 {
  83   struct elf_link_hash_table *htab;
  84   const struct elf_backend_data *bed;
  85   asection *s;
  86
  87   htab = elf_hash_table (info);
  88   bed = get_elf_backend_data (dynobj);
  89
  90   if (!bfd_link_pic (info))
  91     {
  92       s = bfd_make_section_anyway_with_flags (dynobj,
  93                                               bed->default_use_rela_p
  94                                               ? ".rela.plt.unloaded"
  95                                               : ".rel.plt.unloaded",
  96                                               SEC_HAS_CONTENTS | SEC_IN_MEMORY
  97                                               | SEC_READONLY
  98                                               | SEC_LINKER_CREATED);
  99       if (s == NULL
 100           || !bfd_set_section_alignment (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 int
 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 1;
 144 }
 145
 146 /* Copy relocations into the output file.  Fixes up relocations against PLT
 147    entries, then calls the generic routine.  */
 148
 149 bool
 150 elf_vxworks_emit_relocs (bfd *output_bfd,
 151                          asection *input_section,
 152                          Elf_Internal_Shdr *input_rel_hdr,
 153                          Elf_Internal_Rela *internal_relocs,
 154                          struct elf_link_hash_entry **rel_hash)
 155 {
 156   const struct elf_backend_data *bed;
 157   int j;
 158
 159   bed = get_elf_backend_data (output_bfd);
 160
 161   if (output_bfd->flags & (DYNAMIC|EXEC_P))
 162     {
 163       Elf_Internal_Rela *irela;
 164       Elf_Internal_Rela *irelaend;
 165       struct elf_link_hash_entry **hash_ptr;
 166
 167       for (irela = internal_relocs,
 168              irelaend = irela + (NUM_SHDR_ENTRIES (input_rel_hdr)
 169                                  * bed->s->int_rels_per_ext_rel),
 170              hash_ptr = rel_hash;
 171            irela < irelaend;
 172            irela += bed->s->int_rels_per_ext_rel,
 173              hash_ptr++)
 174         {
 175           if (*hash_ptr)
 176             {
 177               (*hash_ptr)->has_reloc = 1;
 178               if ((*hash_ptr)->def_dynamic
 179                   && !(*hash_ptr)->def_regular
 180                   && ((*hash_ptr)->root.type == bfd_link_hash_defined
 181                       || (*hash_ptr)->root.type == bfd_link_hash_defweak)
 182                   && (*hash_ptr)->root.u.def.section->output_section != NULL)
 183                 {
 184                   /* This is a relocation from an executable or shared
 185                      library against a symbol in a different shared
 186                      library.  We are creating a definition in the output
 187                      file but it does not come from any of our normal (.o)
 188                      files. ie. a PLT stub.  Normally this would be a
 189                      relocation against SHN_UNDEF with the VMA of
 190                      the PLT stub.  This upsets the VxWorks loader.
 191                      Convert it to a section-relative relocation.  This
 192                      gets some other symbols (for instance .dynbss), but
 193                      is conservatively correct.  */
 194                   for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
 195                     {
 196                       asection *sec = (*hash_ptr)->root.u.def.section;
 197                       int this_idx = sec->output_section->target_index;
 198
 199                       irela[j].r_info
 200                         = ELF32_R_INFO (this_idx,
 201                                         ELF32_R_TYPE (irela[j].r_info));
 202                       irela[j].r_addend += (*hash_ptr)->root.u.def.value;
 203                       irela[j].r_addend += sec->output_offset;
 204                     }
 205                   /* Stop the generic routine adjusting this entry.  */
 206                   *hash_ptr = NULL;
 207                 }
 208             }
 209         }
 210     }
 211   return _bfd_elf_link_output_relocs (output_bfd, input_section,
 212                                       input_rel_hdr, internal_relocs,
 213                                       rel_hash);
 214 }
 215
 216
 217 /* Set the sh_link and sh_info fields on the static plt relocation secton.  */
 218
 219 bool
 220 elf_vxworks_final_write_processing (bfd *abfd)
 221 {
 222   asection * sec;
 223   struct bfd_elf_section_data *d;
 224
 225   sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
 226   if (!sec)
 227     sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
 228   if (sec)
 229     {
 230       d = elf_section_data (sec);
 231       d->this_hdr.sh_link = elf_onesymtab (abfd);
 232       sec = bfd_get_section_by_name (abfd, ".plt");
 233       if (sec)
 234         d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
 235     }
 236   return _bfd_elf_final_write_processing (abfd);
 237 }
 238
 239 /* Add the dynamic entries required by VxWorks.  These point to the
 240    tls sections.  */
 241
 242 bool
 243 elf_vxworks_add_dynamic_entries (bfd *output_bfd, struct bfd_link_info *info)
 244 {
 245   if (bfd_get_section_by_name (output_bfd, ".tls_data"))
 246     {
 247       if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_START, 0)
 248           || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_SIZE, 0)
 249           || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_DATA_ALIGN, 0))
 250         return false;
 251     }
 252   if (bfd_get_section_by_name (output_bfd, ".tls_vars"))
 253     {
 254       if (!_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_START, 0)
 255           || !_bfd_elf_add_dynamic_entry (info, DT_VX_WRS_TLS_VARS_SIZE, 0))
 256         return false;
 257     }
 258   return true;
 259 }
 260
 261 /* If *DYN is one of the VxWorks-specific dynamic entries, then fill
 262    in the value now  and return TRUE.  Otherwise return FALSE.  */
 263
 264 bool
 265 elf_vxworks_finish_dynamic_entry (bfd *output_bfd, Elf_Internal_Dyn *dyn)
 266 {
 267   asection *sec;
 268
 269   switch (dyn->d_tag)
 270     {
 271     default:
 272       return false;
 273
 274     case DT_VX_WRS_TLS_DATA_START:
 275       sec = bfd_get_section_by_name (output_bfd, ".tls_data");
 276       dyn->d_un.d_ptr = sec->vma;
 277       break;
 278
 279     case DT_VX_WRS_TLS_DATA_SIZE:
 280       sec = bfd_get_section_by_name (output_bfd, ".tls_data");
 281       dyn->d_un.d_val = sec->size;
 282       break;
 283
 284     case DT_VX_WRS_TLS_DATA_ALIGN:
 285       sec = bfd_get_section_by_name (output_bfd, ".tls_data");
 286       dyn->d_un.d_val = (bfd_size_type) 1 << bfd_section_alignment (sec);
 287       break;
 288
 289     case DT_VX_WRS_TLS_VARS_START:
 290       sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
 291       dyn->d_un.d_ptr = sec->vma;
 292       break;
 293
 294     case DT_VX_WRS_TLS_VARS_SIZE:
 295       sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
 296       dyn->d_un.d_val = sec->size;
 297       break;
 298     }
 299   return true;
 300 }
 301
 302 /* Add dynamic tags.  */
 303
 304 bool
 305 _bfd_elf_maybe_vxworks_add_dynamic_tags (bfd *output_bfd,
 306                                          struct bfd_link_info *info,
 307                                          bool need_dynamic_reloc)
 308 {
 309   struct elf_link_hash_table *htab = elf_hash_table (info);
 310   return (_bfd_elf_add_dynamic_tags (output_bfd, info,
 311                                      need_dynamic_reloc)
 312           && (!htab->dynamic_sections_created
 313               || htab->target_os != is_vxworks
 314               || elf_vxworks_add_dynamic_entries (output_bfd, info)));
 315 }