bfd/elf-vxworks.c

   1 /* VxWorks support for ELF
   2    Copyright (C) 2005-2022 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               && (*hash_ptr)->def_dynamic
 177               && !(*hash_ptr)->def_regular
 178               && ((*hash_ptr)->root.type == bfd_link_hash_defined
 179                   || (*hash_ptr)->root.type == bfd_link_hash_defweak)
 180               && (*hash_ptr)->root.u.def.section->output_section != NULL)
 181             {
 182               /* This is a relocation from an executable or shared
 183                  library against a symbol in a different shared
 184                  library.  We are creating a definition in the output
 185                  file but it does not come from any of our normal (.o)
 186                  files. ie. a PLT stub.  Normally this would be a
 187                  relocation against against SHN_UNDEF with the VMA of
 188                  the PLT stub.  This upsets the VxWorks loader.
 189                  Convert it to a section-relative relocation.  This
 190                  gets some other symbols (for instance .dynbss), but
 191                  is conservatively correct.  */
 192               for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
 193                 {
 194                   asection *sec = (*hash_ptr)->root.u.def.section;
 195                   int this_idx = sec->output_section->target_index;
 196
 197                   irela[j].r_info
 198                     = ELF32_R_INFO (this_idx, ELF32_R_TYPE (irela[j].r_info));
 199                   irela[j].r_addend += (*hash_ptr)->root.u.def.value;
 200                   irela[j].r_addend += sec->output_offset;
 201                 }
 202               /* Stop the generic routine adjusting this entry.  */
 203               *hash_ptr = NULL;
 204             }
 205         }
 206     }
 207   return _bfd_elf_link_output_relocs (output_bfd, input_section,
 208                                       input_rel_hdr, internal_relocs,
 209                                       rel_hash);
 210 }
 211
 212
 213 /* Set the sh_link and sh_info fields on the static plt relocation secton.  */
 214
 215 bool
 216 elf_vxworks_final_write_processing (bfd *abfd)
 217 {
 218   asection * sec;
 219   struct bfd_elf_section_data *d;
 220
 221   sec = bfd_get_section_by_name (abfd, ".rel.plt.unloaded");
 222   if (!sec)
 223     sec = bfd_get_section_by_name (abfd, ".rela.plt.unloaded");
 224   if (sec)
 225     {
 226       d = elf_section_data (sec);
 227       d->this_hdr.sh_link = elf_onesymtab (abfd);
 228       sec = bfd_get_section_by_name (abfd, ".plt");
 229       if (sec)
 230         d->this_hdr.sh_info = elf_section_data (sec)->this_idx;
 231     }
 232   return _bfd_elf_final_write_processing (abfd);
 233 }
 234
 235 /* Add the dynamic entries required by VxWorks.  These point to the
 236    tls sections.  */
 237
 238 bool
 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 bool
 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 = (bfd_size_type) 1 << bfd_section_alignment (sec);
 283       break;
 284
 285     case DT_VX_WRS_TLS_VARS_START:
 286       sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
 287       dyn->d_un.d_ptr = sec->vma;
 288       break;
 289
 290     case DT_VX_WRS_TLS_VARS_SIZE:
 291       sec = bfd_get_section_by_name (output_bfd, ".tls_vars");
 292       dyn->d_un.d_val = sec->size;
 293       break;
 294     }
 295   return true;
 296 }
 297
 298 /* Add dynamic tags.  */
 299
 300 bool
 301 _bfd_elf_maybe_vxworks_add_dynamic_tags (bfd *output_bfd,
 302                                          struct bfd_link_info *info,
 303                                          bool need_dynamic_reloc)
 304 {
 305   struct elf_link_hash_table *htab = elf_hash_table (info);
 306   return (_bfd_elf_add_dynamic_tags (output_bfd, info,
 307                                      need_dynamic_reloc)
 308           && (!htab->dynamic_sections_created
 309               || htab->target_os != is_vxworks
 310               || elf_vxworks_add_dynamic_entries (output_bfd, info)));
 311 }