gold/target.cc

   1 // target.cc
   2
   3 // Copyright 2009, 2010 Free Software Foundation, Inc.
   4 // Written by Doug Kwan <dougkwan@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24 #include "elfcpp.h"
  25 #include "dynobj.h"
  26 #include "symtab.h"
  27 #include "output.h"
  28 #include "target.h"
  29
  30 namespace gold
  31 {
  32
  33 // Return whether NAME is a local label name.  This is used to implement the
  34 // --discard-locals options and can be overridden by child classes to
  35 // implement system-specific behaviour.  The logic here is the same as that
  36 // in _bfd_elf_is_local_label_name().
  37
  38 bool
  39 Target::do_is_local_label_name(const char* name) const
  40 {
  41   // Normal local symbols start with ``.L''.
  42   if (name[0] == '.' && name[1] == 'L')
  43     return true;
  44
  45   // At least some SVR4 compilers (e.g., UnixWare 2.1 cc) generate
  46   // DWARF debugging symbols starting with ``..''.
  47   if (name[0] == '.' && name[1] == '.')
  48     return true;
  49
  50   // gcc will sometimes generate symbols beginning with ``_.L_'' when
  51   // emitting DWARF debugging output.  I suspect this is actually a
  52   // small bug in gcc (it calls ASM_OUTPUT_LABEL when it should call
  53   // ASM_GENERATE_INTERNAL_LABEL, and this causes the leading
  54   // underscore to be emitted on some ELF targets).  For ease of use,
  55   // we treat such symbols as local.
  56   if (name[0] == '_' && name[1] == '.' && name[2] == 'L' && name[3] == '_')
  57     return true;
  58
  59   return false;
  60 }
  61
  62 // Implementations of methods Target::do_make_elf_object are almost identical
  63 // except for the address sizes and endianities.  So we extract this
  64 // into a template.
  65
  66 template<int size, bool big_endian>
  67 inline Object*
  68 Target::do_make_elf_object_implementation(
  69     const std::string& name,
  70     Input_file* input_file,
  71     off_t offset,
  72     const elfcpp::Ehdr<size, big_endian>& ehdr)
  73 {
  74   int et = ehdr.get_e_type();
  75   if (et == elfcpp::ET_REL)
  76     {
  77       Sized_relobj<size, big_endian>* obj =
  78         new Sized_relobj<size, big_endian>(name, input_file, offset, ehdr);
  79       obj->setup();
  80       return obj;
  81     }
  82   else if (et == elfcpp::ET_DYN)
  83     {
  84       Sized_dynobj<size, big_endian>* obj =
  85         new Sized_dynobj<size, big_endian>(name, input_file, offset, ehdr);
  86       obj->setup();
  87       return obj;
  88     }
  89   else
  90     {
  91       gold_error(_("%s: unsupported ELF file type %d"),
  92                  name.c_str(), et);
  93       return NULL;
  94     }
  95 }
  96
  97 // Make an ELF object called NAME by reading INPUT_FILE at OFFSET.  EHDR
  98 // is the ELF header of the object.  There are four versions of this
  99 // for different address sizes and endianities.
 100
 101 #ifdef HAVE_TARGET_32_LITTLE
 102 Object*
 103 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 104                            off_t offset, const elfcpp::Ehdr<32, false>& ehdr)
 105 {
 106   return this->do_make_elf_object_implementation<32, false>(name, input_file,
 107                                                             offset, ehdr);
 108 }
 109 #endif
 110
 111 #ifdef HAVE_TARGET_32_BIG
 112 Object*
 113 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 114                            off_t offset, const elfcpp::Ehdr<32, true>& ehdr)
 115 {
 116   return this->do_make_elf_object_implementation<32, true>(name, input_file,
 117                                                            offset, ehdr);
 118 }
 119 #endif
 120
 121 #ifdef HAVE_TARGET_64_LITTLE
 122 Object*
 123 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 124                            off_t offset, const elfcpp::Ehdr<64, false>& ehdr)
 125 {
 126   return this->do_make_elf_object_implementation<64, false>(name, input_file,
 127                                                             offset, ehdr);
 128 }
 129 #endif
 130
 131 #ifdef HAVE_TARGET_64_BIG
 132 Object*
 133 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 134                            off_t offset, const elfcpp::Ehdr<64, true>& ehdr)
 135 {
 136   return this->do_make_elf_object_implementation<64, true>(name, input_file,
 137                                                            offset, ehdr);
 138 }
 139 #endif
 140
 141 Output_section*
 142 Target::do_make_output_section(const char* name, elfcpp::Elf_Word type,
 143                                elfcpp::Elf_Xword flags)
 144 {
 145   return new Output_section(name, type, flags);
 146 }
 147
 148 // Default for whether a reloc is a call to a non-split function is
 149 // whether the symbol is a function.
 150
 151 bool
 152 Target::do_is_call_to_non_split(const Symbol* sym, unsigned int) const
 153 {
 154   return sym->type() == elfcpp::STT_FUNC;
 155 }
 156
 157 // Default conversion for -fsplit-stack is to give an error.
 158
 159 void
 160 Target::do_calls_non_split(Relobj* object, unsigned int, section_offset_type,
 161                            section_size_type, unsigned char*, section_size_type,
 162                            std::string*, std::string*) const
 163 {
 164   static bool warned;
 165   if (!warned)
 166     {
 167       gold_error(_("linker does not include stack split support "
 168                    "required by %s"),
 169                  object->name().c_str());
 170       warned = true;
 171     }
 172 }
 173
 174 //  Return whether BYTES/LEN matches VIEW/VIEW_SIZE at OFFSET.
 175
 176 bool
 177 Target::match_view(const unsigned char* view, section_size_type view_size,
 178                    section_offset_type offset, const char* bytes,
 179                    size_t len) const
 180 {
 181   if (offset + len > view_size)
 182     return false;
 183   return memcmp(view + offset, bytes, len) == 0;
 184 }
 185
 186 // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET
 187 // for LEN bytes.
 188
 189 void
 190 Target::set_view_to_nop(unsigned char* view, section_size_type view_size,
 191                         section_offset_type offset, size_t len) const
 192 {
 193   gold_assert(offset >= 0 && offset + len <= view_size);
 194   if (!this->has_code_fill())
 195     memset(view + offset, 0, len);
 196   else
 197     {
 198       std::string fill = this->code_fill(len);
 199       memcpy(view + offset, fill.data(), len);
 200     }
 201 }
 202
 203 } // End namespace gold.