ld/ldelfgen.c

   1 /* Emulation code used by all ELF targets.
   2    Copyright (C) 1991-2020 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 "ldelfgen.h"
  32
  33 void
  34 ldelf_map_segments (bfd_boolean need_layout)
  35 {
  36   int tries = 10;
  37
  38   do
  39     {
  40       lang_relax_sections (need_layout);
  41       need_layout = FALSE;
  42
  43       if (link_info.output_bfd->xvec->flavour == bfd_target_elf_flavour
  44           && !bfd_link_relocatable (&link_info))
  45         {
  46           bfd_size_type phdr_size;
  47
  48           phdr_size = elf_program_header_size (link_info.output_bfd);
  49           /* If we don't have user supplied phdrs, throw away any
  50              previous linker generated program headers.  */
  51           if (lang_phdr_list == NULL)
  52             elf_seg_map (link_info.output_bfd) = NULL;
  53           if (!_bfd_elf_map_sections_to_segments (link_info.output_bfd,
  54                                                   &link_info))
  55             einfo (_("%F%P: map sections to segments failed: %E\n"));
  56
  57           if (phdr_size != elf_program_header_size (link_info.output_bfd))
  58             {
  59               if (tries > 6)
  60                 /* The first few times we allow any change to
  61                    phdr_size .  */
  62                 need_layout = TRUE;
  63               else if (phdr_size
  64                        < elf_program_header_size (link_info.output_bfd))
  65                 /* After that we only allow the size to grow.  */
  66                 need_layout = TRUE;
  67               else
  68                 elf_program_header_size (link_info.output_bfd) = phdr_size;
  69             }
  70         }
  71     }
  72   while (need_layout && --tries);
  73
  74   if (tries == 0)
  75     einfo (_("%F%P: looping in map_segments"));
  76
  77   if (link_info.output_bfd->xvec->flavour == bfd_target_elf_flavour
  78       && lang_phdr_list == NULL)
  79     {
  80       /* If we don't have user supplied phdrs, strip zero-sized dynamic
  81          sections and regenerate program headers.  */
  82       const struct elf_backend_data *bed
  83         = get_elf_backend_data (link_info.output_bfd);
  84       if (bed->elf_backend_strip_zero_sized_dynamic_sections
  85           && !bed->elf_backend_strip_zero_sized_dynamic_sections
  86                 (&link_info))
  87           einfo (_("%F%P: failed to strip zero-sized dynamic sections"));
  88     }
  89 }
  90
  91 /* We want to emit CTF early if and only if we are not targetting ELF with this
  92    invocation.  */
  93
  94 int
  95 ldelf_emit_ctf_early (void)
  96 {
  97   if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
  98     return 0;
  99   return 1;
 100 }
 101
 102 /* Callbacks used to map from bfd types to libctf types, under libctf's
 103    control.  */
 104
 105 struct ctf_strsym_iter_cb_arg
 106 {
 107   struct elf_sym_strtab *syms;
 108   bfd_size_type symcount;
 109   struct elf_strtab_hash *symstrtab;
 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_strsym_iter_cb_arg *arg =
 124     (struct ctf_strsym_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->symstrtab))
 131     {
 132       arg->next_i = 0;
 133       return NULL;
 134     }
 135
 136   ret = _bfd_elf_strtab_str (arg->symstrtab, 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 /* Return symbols from the symbol table to libctf, one by one.  We assume (and
 148    assert) that the symbols in the elf_link_hash_table are in strictly ascending
 149    order, and that none will be added in between existing ones.  Returns NULL
 150    when iteration is complete.  */
 151
 152 static struct ctf_link_sym *
 153 ldelf_ctf_symbols_iter_cb (struct ctf_link_sym *dest,
 154                                            void *arg_)
 155 {
 156   struct ctf_strsym_iter_cb_arg *arg =
 157     (struct ctf_strsym_iter_cb_arg *) arg_;
 158
 159   if (arg->next_i > arg->symcount)
 160     {
 161       arg->next_i = 0;
 162       arg->next_idx = 0;
 163       return NULL;
 164     }
 165
 166   ASSERT (arg->syms[arg->next_i].dest_index == arg->next_idx);
 167   dest->st_name = _bfd_elf_strtab_str (arg->symstrtab, arg->next_i, NULL);
 168   dest->st_shndx = arg->syms[arg->next_i].sym.st_shndx;
 169   dest->st_type = ELF_ST_TYPE (arg->syms[arg->next_i].sym.st_info);
 170   dest->st_value = arg->syms[arg->next_i].sym.st_value;
 171   arg->next_i++;
 172   return dest;
 173 }
 174
 175 void
 176 ldelf_examine_strtab_for_ctf
 177   (struct ctf_file *ctf_output, struct elf_sym_strtab *syms,
 178    bfd_size_type symcount, struct elf_strtab_hash *symstrtab)
 179 {
 180   struct ctf_strsym_iter_cb_arg args = { syms, symcount, symstrtab,
 181                                           0, 0 };
 182    if (!ctf_output)
 183      return;
 184
 185    if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour
 186        && !bfd_link_relocatable (&link_info))
 187     {
 188       if (ctf_link_add_strtab (ctf_output, ldelf_ctf_strtab_iter_cb,
 189                                &args) < 0)
 190         einfo (_("%F%P: warning: CTF strtab association failed; strings will "
 191                  "not be shared: %s\n"),
 192                ctf_errmsg (ctf_errno (ctf_output)));
 193
 194       if (ctf_link_shuffle_syms (ctf_output, ldelf_ctf_symbols_iter_cb,
 195                                  &args) < 0)
 196         einfo (_("%F%P: warning: CTF symbol shuffling failed; slight space "
 197                  "cost: %s\n"), ctf_errmsg (ctf_errno (ctf_output)));
 198     }
 199 }