ld/ldelfgen.c

   1 /* Emulation code used by all ELF targets.
   2    Copyright (C) 1991-2019 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
  78 /* We want to emit CTF early if and only if we are not targetting ELF with this
  79    invocation.  */
  80
  81 int
  82 ldelf_emit_ctf_early (void)
  83 {
  84   if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour)
  85     return 0;
  86   return 1;
  87 }
  88
  89 /* Callbacks used to map from bfd types to libctf types, under libctf's
  90    control.  */
  91
  92 struct ctf_strsym_iter_cb_arg
  93 {
  94   struct elf_sym_strtab *syms;
  95   bfd_size_type symcount;
  96   struct elf_strtab_hash *symstrtab;
  97   size_t next_i;
  98   size_t next_idx;
  99 };
 100
 101 /* Return strings from the strtab to libctf, one by one.  Returns NULL when
 102    iteration is complete.  */
 103
 104 static const char *
 105 ldelf_ctf_strtab_iter_cb (uint32_t *offset, void *arg_)
 106 {
 107   bfd_size_type off;
 108   const char *ret;
 109
 110   struct ctf_strsym_iter_cb_arg *arg =
 111     (struct ctf_strsym_iter_cb_arg *) arg_;
 112
 113   /* There is no zeroth string.  */
 114   if (arg->next_i == 0)
 115     arg->next_i = 1;
 116
 117   if (arg->next_i >= _bfd_elf_strtab_len (arg->symstrtab))
 118     {
 119       arg->next_i = 0;
 120       return NULL;
 121     }
 122
 123   ret = _bfd_elf_strtab_str (arg->symstrtab, arg->next_i++, &off);
 124   *offset = off;
 125
 126   /* If we've overflowed, we cannot share any further strings: the CTF
 127      format cannot encode strings with such high offsets.  */
 128   if (*offset != off)
 129     return NULL;
 130
 131   return ret;
 132 }
 133
 134 /* Return symbols from the symbol table to libctf, one by one.  We assume (and
 135    assert) that the symbols in the elf_link_hash_table are in strictly ascending
 136    order, and that none will be added in between existing ones.  Returns NULL
 137    when iteration is complete.  */
 138
 139 static struct ctf_link_sym *
 140 ldelf_ctf_symbols_iter_cb (struct ctf_link_sym *dest,
 141                                            void *arg_)
 142 {
 143   struct ctf_strsym_iter_cb_arg *arg =
 144     (struct ctf_strsym_iter_cb_arg *) arg_;
 145
 146   if (arg->next_i > arg->symcount)
 147     {
 148       arg->next_i = 0;
 149       arg->next_idx = 0;
 150       return NULL;
 151     }
 152
 153   ASSERT (arg->syms[arg->next_i].dest_index == arg->next_idx);
 154   dest->st_name = _bfd_elf_strtab_str (arg->symstrtab, arg->next_i, NULL);
 155   dest->st_shndx = arg->syms[arg->next_i].sym.st_shndx;
 156   dest->st_type = ELF_ST_TYPE (arg->syms[arg->next_i].sym.st_info);
 157   dest->st_value = arg->syms[arg->next_i].sym.st_value;
 158   arg->next_i++;
 159   return dest;
 160 }
 161
 162 void
 163 ldelf_examine_strtab_for_ctf
 164   (struct ctf_file *ctf_output, struct elf_sym_strtab *syms,
 165    bfd_size_type symcount, struct elf_strtab_hash *symstrtab)
 166 {
 167   struct ctf_strsym_iter_cb_arg args = { syms, symcount, symstrtab,
 168                                           0, 0 };
 169    if (!ctf_output)
 170      return;
 171
 172    if (bfd_get_flavour (link_info.output_bfd) == bfd_target_elf_flavour
 173        && !bfd_link_relocatable (&link_info))
 174     {
 175       if (ctf_link_add_strtab (ctf_output, ldelf_ctf_strtab_iter_cb,
 176                                &args) < 0)
 177         einfo (_("%F%P: warning: CTF strtab association failed; strings will "
 178                  "not be shared: %s\n"),
 179                ctf_errmsg (ctf_errno (ctf_output)));
 180
 181       if (ctf_link_shuffle_syms (ctf_output, ldelf_ctf_symbols_iter_cb,
 182                                  &args) < 0)
 183         einfo (_("%F%P: warning: CTF symbol shuffling failed; slight space "
 184                  "cost: %s\n"), ctf_errmsg (ctf_errno (ctf_output)));
 185     }
 186 }