ld/ldelfgen.c

   1 /* Emulation code used by all ELF targets.
   2    Copyright (C) 1991-2021 Free Software Foundation, Inc.
   3
   4    This file is part of the GNU Binutils.
   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., 51 Franklin Street - Fifth Floor, Boston,
  19    MA 02110-1301, USA.  */
  20
  21 #include "sysdep.h"
  22 #include "bfd.h"
  23 #include "bfdlink.h"
  24 #include "ctf-api.h"
  25 #include "ld.h"
  26 #include "ldmain.h"
  27 #include "ldmisc.h"
  28 #include "ldexp.h"
  29 #include "ldlang.h"
  30 #include "elf-bfd.h"
  31 #include "elf/internal.h"
  32 #include "ldelfgen.h"
  33
  34 void
  35 ldelf_map_segments (bfd_boolean need_layout)
  36 {
  37   int tries = 10;
  38
  39   do
  40     {
  41       lang_relax_sections (need_layout);
  42       need_layout = FALSE;
  43
  44       if (link_info.output_bfd->xvec->flavour == bfd_target_elf_flavour
  45           && !bfd_link_relocatable (&link_info))
  46         {
  47           bfd_size_type phdr_size;
  48
  49           phdr_size = elf_program_header_size (link_info.output_bfd);
  50           /* If we don't have user supplied phdrs, throw away any
  51              previous linker generated program headers.  */
  52           if (lang_phdr_list == NULL)
  53             elf_seg_map (link_info.output_bfd) = NULL;
  54           if (!_bfd_elf_map_sections_to_segments (link_info.output_bfd,
  55                                                   &link_info))
  56             einfo (_("%F%P: map sections to segments failed: %E\n"));
  57
  58           if (phdr_size != elf_program_header_size (link_info.output_bfd))
  59             {
  60               if (tries > 6)
  61                 /* The first few times we allow any change to
  62                    phdr_size .  */
  63                 need_layout = TRUE;
  64               else if (phdr_size
  65                        < elf_program_header_size (link_info.output_bfd))
  66                 /* After that we only allow the size to grow.  */
  67                 need_layout = TRUE;
  68               else
  69                 elf_program_header_size (link_info.output_bfd) = phdr_size;
  70             }
  71         }
  72     }
  73   while (need_layout && --tries);
  74
  75   if (tries == 0)
  76     einfo (_("%F%P: looping in map_segments"));
  77
  78   if (link_info.output_bfd->xvec->flavour == bfd_target_elf_flavour
  79       && lang_phdr_list == NULL)
  80     {
  81       /* If we don't have user supplied phdrs, strip zero-sized dynamic
  82          sections and regenerate program headers.  */
  83       const struct elf_backend_data *bed
  84         = get_elf_backend_data (link_info.output_bfd);
  85       if (bed->elf_backend_strip_zero_sized_dynamic_sections
  86           && !bed->elf_backend_strip_zero_sized_dynamic_sections
  87                 (&link_info))
  88           einfo (_("%F%P: failed to strip zero-sized dynamic sections"));
  89     }
  90 }
  91
  92 #ifdef ENABLE_LIBCTF
  93 /* We want to emit CTF early if and only if we are not targetting ELF with this
  94    invocation.  */
  95
  96 int
  97 ldelf_emit_ctf_early (void)
  98 {
  99   if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
 100     return 0;
 101   return 1;
 102 }
 103
 104 /* Callbacks used to map from bfd types to libctf types, under libctf's
 105    control.  */
 106
 107 struct ctf_strtab_iter_cb_arg
 108 {
 109   struct elf_strtab_hash *strtab;
 110   size_t next_i;
 111   size_t next_idx;
 112 };
 113
 114 /* Return strings from the strtab to libctf, one by one.  Returns NULL when
 115    iteration is complete.  */
 116
 117 static const char *
 118 ldelf_ctf_strtab_iter_cb (uint32_t *offset, void *arg_)
 119 {
 120   bfd_size_type off;
 121   const char *ret;
 122
 123   struct ctf_strtab_iter_cb_arg *arg =
 124     (struct ctf_strtab_iter_cb_arg *) arg_;
 125
 126   /* There is no zeroth string.  */
 127   if (arg->next_i == 0)
 128     arg->next_i = 1;
 129
 130   if (arg->next_i >= _bfd_elf_strtab_len (arg->strtab))
 131     {
 132       arg->next_i = 0;
 133       return NULL;
 134     }
 135
 136   ret = _bfd_elf_strtab_str (arg->strtab, arg->next_i++, &off);
 137   *offset = off;
 138
 139   /* If we've overflowed, we cannot share any further strings: the CTF
 140      format cannot encode strings with such high offsets.  */
 141   if (*offset != off)
 142     return NULL;
 143
 144   return ret;
 145 }
 146
 147 void
 148 ldelf_acquire_strings_for_ctf
 149   (struct ctf_dict *ctf_output, struct elf_strtab_hash *strtab)
 150 {
 151   struct ctf_strtab_iter_cb_arg args = { strtab, 0, 0 };
 152   if (!ctf_output)
 153     return;
 154
 155   if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
 156     {
 157       if (ctf_link_add_strtab (ctf_output, ldelf_ctf_strtab_iter_cb,
 158                                &args) < 0)
 159         einfo (_("%F%P: warning: CTF strtab association failed; strings will "
 160                  "not be shared: %s\n"),
 161                ctf_errmsg (ctf_errno (ctf_output)));
 162     }
 163 }
 164
 165 void
 166 ldelf_new_dynsym_for_ctf (struct ctf_dict *ctf_output, int symidx,
 167                           struct elf_internal_sym *sym)
 168 {
 169   ctf_link_sym_t lsym;
 170
 171   if (!ctf_output)
 172      return;
 173
 174   /* New symbol.  */
 175   if (sym != NULL)
 176     {
 177       lsym.st_name = NULL;
 178       lsym.st_nameidx = sym->st_name;
 179       lsym.st_nameidx_set = 1;
 180       lsym.st_symidx = symidx;
 181       lsym.st_shndx = sym->st_shndx;
 182       lsym.st_type = ELF_ST_TYPE (sym->st_info);
 183       lsym.st_value = sym->st_value;
 184       if (ctf_link_add_linker_symbol (ctf_output, &lsym) < 0)
 185         {
 186           einfo (_("%F%P: warning: CTF symbol addition failed; CTF will "
 187                    "not be tied to symbols: %s\n"),
 188                  ctf_errmsg (ctf_errno (ctf_output)));
 189         }
 190     }
 191   else
 192     {
 193       /* Shuffle all the symbols.  */
 194
 195       if (ctf_link_shuffle_syms (ctf_output) < 0)
 196         einfo (_("%F%P: warning: CTF symbol shuffling failed; CTF will "
 197                  "not be tied to symbols: %s\n"),
 198                ctf_errmsg (ctf_errno (ctf_output)));
 199     }
 200 }
 201 #else
 202 int
 203 ldelf_emit_ctf_early (void)
 204 {
 205   return 0;
 206 }
 207
 208 void
 209 ldelf_acquire_strings_for_ctf (struct ctf_dict *ctf_output ATTRIBUTE_UNUSED,
 210                                struct elf_strtab_hash *strtab ATTRIBUTE_UNUSED)
 211 {}
 212 void
 213 ldelf_new_dynsym_for_ctf (struct ctf_dict *ctf_output ATTRIBUTE_UNUSED,
 214                           int symidx ATTRIBUTE_UNUSED,
 215                           struct elf_internal_sym *sym ATTRIBUTE_UNUSED)
 216 {}
 217 #endif