gold/target.cc

   1 // target.cc -- target support for gold.
   2
   3 // Copyright (C) 2009-2016 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   // ET_EXEC files are valid input for --just-symbols/-R,
  76   // and we treat them as relocatable objects.
  77   if (et == elfcpp::ET_REL
  78       || (et == elfcpp::ET_EXEC && input_file->just_symbols()))
  79     {
  80       Sized_relobj_file<size, big_endian>* obj =
  81         new Sized_relobj_file<size, big_endian>(name, input_file, offset, ehdr);
  82       obj->setup();
  83       return obj;
  84     }
  85   else if (et == elfcpp::ET_DYN)
  86     {
  87       Sized_dynobj<size, big_endian>* obj =
  88         new Sized_dynobj<size, big_endian>(name, input_file, offset, ehdr);
  89       obj->setup();
  90       return obj;
  91     }
  92   else
  93     {
  94       gold_error(_("%s: unsupported ELF file type %d"),
  95                  name.c_str(), et);
  96       return NULL;
  97     }
  98 }
  99
 100 // Make an ELF object called NAME by reading INPUT_FILE at OFFSET.  EHDR
 101 // is the ELF header of the object.  There are four versions of this
 102 // for different address sizes and endianities.
 103
 104 #ifdef HAVE_TARGET_32_LITTLE
 105 Object*
 106 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 107                            off_t offset, const elfcpp::Ehdr<32, false>& ehdr)
 108 {
 109   return this->do_make_elf_object_implementation<32, false>(name, input_file,
 110                                                             offset, ehdr);
 111 }
 112 #endif
 113
 114 #ifdef HAVE_TARGET_32_BIG
 115 Object*
 116 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 117                            off_t offset, const elfcpp::Ehdr<32, true>& ehdr)
 118 {
 119   return this->do_make_elf_object_implementation<32, true>(name, input_file,
 120                                                            offset, ehdr);
 121 }
 122 #endif
 123
 124 #ifdef HAVE_TARGET_64_LITTLE
 125 Object*
 126 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 127                            off_t offset, const elfcpp::Ehdr<64, false>& ehdr)
 128 {
 129   return this->do_make_elf_object_implementation<64, false>(name, input_file,
 130                                                             offset, ehdr);
 131 }
 132 #endif
 133
 134 #ifdef HAVE_TARGET_64_BIG
 135 Object*
 136 Target::do_make_elf_object(const std::string& name, Input_file* input_file,
 137                            off_t offset, const elfcpp::Ehdr<64, true>& ehdr)
 138 {
 139   return this->do_make_elf_object_implementation<64, true>(name, input_file,
 140                                                            offset, ehdr);
 141 }
 142 #endif
 143
 144 Output_section*
 145 Target::do_make_output_section(const char* name, elfcpp::Elf_Word type,
 146                                elfcpp::Elf_Xword flags)
 147 {
 148   return new Output_section(name, type, flags);
 149 }
 150
 151 // Default for whether a reloc is a call to a non-split function is
 152 // whether the symbol is a function.
 153
 154 bool
 155 Target::do_is_call_to_non_split(const Symbol* sym, const unsigned char*) const
 156 {
 157   return sym->type() == elfcpp::STT_FUNC;
 158 }
 159
 160 // Default conversion for -fsplit-stack is to give an error.
 161
 162 void
 163 Target::do_calls_non_split(Relobj* object, unsigned int, section_offset_type,
 164                            section_size_type, const unsigned char*, size_t,
 165                            unsigned char*, section_size_type,
 166                            std::string*, std::string*) const
 167 {
 168   static bool warned;
 169   if (!warned)
 170     {
 171       gold_error(_("linker does not include stack split support "
 172                    "required by %s"),
 173                  object->name().c_str());
 174       warned = true;
 175     }
 176 }
 177
 178 //  Return whether BYTES/LEN matches VIEW/VIEW_SIZE at OFFSET.
 179
 180 bool
 181 Target::match_view(const unsigned char* view, section_size_type view_size,
 182                    section_offset_type offset, const char* bytes,
 183                    size_t len) const
 184 {
 185   if (offset + len > view_size)
 186     return false;
 187   return memcmp(view + offset, bytes, len) == 0;
 188 }
 189
 190 // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET
 191 // for LEN bytes.
 192
 193 void
 194 Target::set_view_to_nop(unsigned char* view, section_size_type view_size,
 195                         section_offset_type offset, size_t len) const
 196 {
 197   gold_assert(offset >= 0 && offset + len <= view_size);
 198   if (!this->has_code_fill())
 199     memset(view + offset, 0, len);
 200   else
 201     {
 202       std::string fill = this->code_fill(len);
 203       memcpy(view + offset, fill.data(), len);
 204     }
 205 }
 206
 207 // Return address and size to plug into eh_frame FDEs associated with a PLT.
 208 void
 209 Target::do_plt_fde_location(const Output_data* plt, unsigned char*,
 210                             uint64_t* address, off_t* len) const
 211 {
 212   *address = plt->address();
 213   *len = plt->data_size();
 214 }
 215
 216 // Class Sized_target.
 217
 218 // Set the EI_OSABI field of the ELF header if requested.
 219
 220 template<int size, bool big_endian>
 221 void
 222 Sized_target<size, big_endian>::do_adjust_elf_header(unsigned char* view,
 223                                                      int len)
 224 {
 225   elfcpp::ELFOSABI osabi = this->osabi();
 226   if (osabi != elfcpp::ELFOSABI_NONE)
 227     {
 228       gold_assert(len == elfcpp::Elf_sizes<size>::ehdr_size);
 229
 230       elfcpp::Ehdr<size, big_endian> ehdr(view);
 231       unsigned char e_ident[elfcpp::EI_NIDENT];
 232       memcpy(e_ident, ehdr.get_e_ident(), elfcpp::EI_NIDENT);
 233
 234       e_ident[elfcpp::EI_OSABI] = osabi;
 235
 236       elfcpp::Ehdr_write<size, big_endian> oehdr(view);
 237       oehdr.put_e_ident(e_ident);
 238     }
 239 }
 240
 241 #ifdef HAVE_TARGET_32_LITTLE
 242 template
 243 class Sized_target<32, false>;
 244 #endif
 245
 246 #ifdef HAVE_TARGET_32_BIG
 247 template
 248 class Sized_target<32, true>;
 249 #endif
 250
 251 #ifdef HAVE_TARGET_64_LITTLE
 252 template
 253 class Sized_target<64, false>;
 254 #endif
 255
 256 #ifdef HAVE_TARGET_64_BIG
 257 template
 258 class Sized_target<64, true>;
 259 #endif
 260
 261 } // End namespace gold.