gold/binary.cc

   1 // binary.cc -- binary input files for gold
   2
   3 // Copyright (C) 2008-2018 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@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
  25 #include <cerrno>
  26 #include <cstring>
  27
  28 #include "elfcpp.h"
  29 #include "stringpool.h"
  30 #include "fileread.h"
  31 #include "output.h"
  32 #include "binary.h"
  33
  34 // safe-ctype.h interferes with macros defined by the system <ctype.h>.
  35 // Some C++ system headers might include <ctype.h> and rely on its macro
  36 // definitions being intact.  So make sure that safe-ctype.h is included
  37 // only after any C++ system headers, whether directly here (above) or via
  38 // other local header files (e.g. #include <string> in "binary.h").
  39 #include "safe-ctype.h"
  40
  41 // Support for reading binary files as input.  These become blobs in
  42 // the final output.  These files are treated as though they have a
  43 // single .data section and define three symbols:
  44 // _binary_FILENAME_start, _binary_FILENAME_end, _binary_FILENAME_size.
  45 // The FILENAME is the name of the input file, with any
  46 // non-alphanumeric character changed to an underscore.
  47
  48 // We implement this by creating an ELF file in memory.
  49
  50 namespace gold
  51 {
  52
  53 // class Binary_to_elf.
  54
  55 Binary_to_elf::Binary_to_elf(elfcpp::EM machine, int size, bool big_endian,
  56                              const std::string& filename)
  57   : elf_machine_(machine), size_(size), big_endian_(big_endian),
  58     filename_(filename), data_(NULL), filesize_(0)
  59 {
  60 }
  61
  62 Binary_to_elf::~Binary_to_elf()
  63 {
  64   if (this->data_ != NULL)
  65     delete[] this->data_;
  66 }
  67
  68 // Given FILENAME, create a buffer which looks like an ELF file with
  69 // the contents of FILENAME as the contents of the only section.  The
  70 // TASK parameters is mainly for debugging, and records who holds
  71 // locks.
  72
  73 bool
  74 Binary_to_elf::convert(const Task* task)
  75 {
  76   if (this->size_ == 32)
  77     {
  78       if (!this->big_endian_)
  79         {
  80 #ifdef HAVE_TARGET_32_LITTLE
  81           return this->sized_convert<32, false>(task);
  82 #else
  83           gold_unreachable();
  84 #endif
  85         }
  86       else
  87         {
  88 #ifdef HAVE_TARGET_32_BIG
  89           return this->sized_convert<32, true>(task);
  90 #else
  91           gold_unreachable();
  92 #endif
  93         }
  94     }
  95   else if (this->size_ == 64)
  96     {
  97       if (!this->big_endian_)
  98         {
  99 #ifdef HAVE_TARGET_64_LITTLE
 100           return this->sized_convert<64, false>(task);
 101 #else
 102           gold_unreachable();
 103 #endif
 104         }
 105       else
 106         {
 107 #ifdef HAVE_TARGET_64_BIG
 108           return this->sized_convert<64, true>(task);
 109 #else
 110           gold_unreachable();
 111 #endif
 112         }
 113     }
 114   else
 115     gold_unreachable();
 116 }
 117
 118 // We are going to create:
 119 // * The ELF file header.
 120 // * Five sections: null section, .data, .symtab, .strtab, .shstrtab
 121 // * The contents of the file.
 122 // * Four symbols: null, begin, end, size.
 123 // * Three symbol names.
 124 // * Four section names.
 125
 126 template<int size, bool big_endian>
 127 bool
 128 Binary_to_elf::sized_convert(const Task* task)
 129 {
 130   // Read the input file.
 131
 132   File_read f;
 133   if (!f.open(task, this->filename_))
 134     {
 135       gold_error(_("cannot open %s: %s:"), this->filename_.c_str(),
 136                  strerror(errno));
 137       return false;
 138     }
 139
 140   section_size_type filesize = convert_to_section_size_type(f.filesize());
 141   const unsigned char* fileview;
 142   if (filesize == 0)
 143     fileview = NULL;
 144   else
 145     fileview = f.get_view(0, 0, filesize, false, false);
 146
 147   unsigned int align;
 148   if (size == 32)
 149     align = 4;
 150   else if (size == 64)
 151     align = 8;
 152   else
 153     gold_unreachable();
 154   section_size_type aligned_filesize = align_address(filesize, align);
 155
 156   // Build the stringpool for the symbol table.
 157
 158   std::string mangled_name = this->filename_;
 159   for (std::string::iterator p = mangled_name.begin();
 160        p != mangled_name.end();
 161        ++p)
 162     if (!ISALNUM(*p))
 163       *p = '_';
 164   mangled_name = "_binary_" + mangled_name;
 165   std::string start_symbol_name = mangled_name + "_start";
 166   std::string end_symbol_name = mangled_name + "_end";
 167   std::string size_symbol_name = mangled_name + "_size";
 168
 169   Stringpool strtab;
 170   strtab.add(start_symbol_name.c_str(), false, NULL);
 171   strtab.add(end_symbol_name.c_str(), false, NULL);
 172   strtab.add(size_symbol_name.c_str(), false, NULL);
 173   strtab.set_string_offsets();
 174
 175   // Build the stringpool for the section name table.
 176
 177   Stringpool shstrtab;
 178   shstrtab.add(".data", false, NULL);
 179   shstrtab.add(".symtab", false, NULL);
 180   shstrtab.add(".strtab", false, NULL);
 181   shstrtab.add(".shstrtab", false, NULL);
 182   shstrtab.set_string_offsets();
 183
 184   // Work out the size of the generated file, and the offsets of the
 185   // various sections, and allocate a buffer.
 186
 187   const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
 188
 189   size_t output_size = (elfcpp::Elf_sizes<size>::ehdr_size
 190                         + 5 * elfcpp::Elf_sizes<size>::shdr_size);
 191   size_t data_offset = output_size;
 192   output_size += aligned_filesize;
 193   size_t symtab_offset = output_size;
 194   output_size += 4 * sym_size;
 195   size_t strtab_offset = output_size;
 196   output_size += strtab.get_strtab_size();
 197   size_t shstrtab_offset = output_size;
 198   output_size += shstrtab.get_strtab_size();
 199
 200   unsigned char* buffer = new unsigned char[output_size];
 201
 202   // Write out the data.
 203
 204   unsigned char* pout = buffer;
 205
 206   this->write_file_header<size, big_endian>(&pout);
 207
 208   this->write_section_header<size, big_endian>("", &shstrtab, elfcpp::SHT_NULL,
 209                                                0, 0, 0, 0, 0,
 210                                                0, 0, &pout);
 211   // Having the section be named ".data", having it be writable, and
 212   // giving it an alignment of 1 is because the GNU linker does it
 213   // that way, and existing linker script expect it.
 214   this->write_section_header<size, big_endian>(".data", &shstrtab,
 215                                                elfcpp::SHT_PROGBITS,
 216                                                (elfcpp::SHF_ALLOC
 217                                                 | elfcpp::SHF_WRITE),
 218                                                data_offset,
 219                                                filesize, 0, 0,
 220                                                1, 0, &pout);
 221   this->write_section_header<size, big_endian>(".symtab", &shstrtab,
 222                                                elfcpp::SHT_SYMTAB,
 223                                                0, symtab_offset, 4 * sym_size,
 224                                                3, 1, align, sym_size, &pout);
 225   this->write_section_header<size, big_endian>(".strtab", &shstrtab,
 226                                                elfcpp::SHT_STRTAB,
 227                                                0, strtab_offset,
 228                                                strtab.get_strtab_size(),
 229                                                0, 0, 1, 0, &pout);
 230   this->write_section_header<size, big_endian>(".shstrtab", &shstrtab,
 231                                                elfcpp::SHT_STRTAB,
 232                                                0, shstrtab_offset,
 233                                                shstrtab.get_strtab_size(),
 234                                                0, 0, 1, 0, &pout);
 235
 236   if (filesize > 0)
 237     {
 238       memcpy(pout, fileview, filesize);
 239       pout += filesize;
 240       memset(pout, 0, aligned_filesize - filesize);
 241       pout += aligned_filesize - filesize;
 242     }
 243
 244   this->write_symbol<size, big_endian>("", &strtab, 0, 0, 0, &pout);
 245   this->write_symbol<size, big_endian>(start_symbol_name, &strtab, 0, filesize,
 246                                        1, &pout);
 247   this->write_symbol<size, big_endian>(end_symbol_name, &strtab, filesize, 0,
 248                                        1, &pout);
 249   this->write_symbol<size, big_endian>(size_symbol_name, &strtab, filesize, 0,
 250                                        elfcpp::SHN_ABS, &pout);
 251
 252   strtab.write_to_buffer(pout, strtab.get_strtab_size());
 253   pout += strtab.get_strtab_size();
 254
 255   shstrtab.write_to_buffer(pout, shstrtab.get_strtab_size());
 256   pout += shstrtab.get_strtab_size();
 257
 258   gold_assert(static_cast<size_t>(pout - buffer) == output_size);
 259
 260   this->data_ = buffer;
 261   this->filesize_ = output_size;
 262
 263   f.unlock(task);
 264
 265   return true;
 266 }
 267
 268 // Write out the file header.
 269
 270 template<int size, bool big_endian>
 271 void
 272 Binary_to_elf::write_file_header(unsigned char** ppout)
 273 {
 274   elfcpp::Ehdr_write<size, big_endian> oehdr(*ppout);
 275
 276   unsigned char e_ident[elfcpp::EI_NIDENT];
 277   memset(e_ident, 0, elfcpp::EI_NIDENT);
 278   e_ident[elfcpp::EI_MAG0] = elfcpp::ELFMAG0;
 279   e_ident[elfcpp::EI_MAG1] = elfcpp::ELFMAG1;
 280   e_ident[elfcpp::EI_MAG2] = elfcpp::ELFMAG2;
 281   e_ident[elfcpp::EI_MAG3] = elfcpp::ELFMAG3;
 282   if (size == 32)
 283     e_ident[elfcpp::EI_CLASS] = elfcpp::ELFCLASS32;
 284   else if (size == 64)
 285     e_ident[elfcpp::EI_CLASS] = elfcpp::ELFCLASS64;
 286   else
 287     gold_unreachable();
 288   e_ident[elfcpp::EI_DATA] = (big_endian
 289                               ? elfcpp::ELFDATA2MSB
 290                               : elfcpp::ELFDATA2LSB);
 291   e_ident[elfcpp::EI_VERSION] = elfcpp::EV_CURRENT;
 292   oehdr.put_e_ident(e_ident);
 293
 294   oehdr.put_e_type(elfcpp::ET_REL);
 295   oehdr.put_e_machine(this->elf_machine_);
 296   oehdr.put_e_version(elfcpp::EV_CURRENT);
 297   oehdr.put_e_entry(0);
 298   oehdr.put_e_phoff(0);
 299   oehdr.put_e_shoff(elfcpp::Elf_sizes<size>::ehdr_size);
 300   oehdr.put_e_flags(0);
 301   oehdr.put_e_ehsize(elfcpp::Elf_sizes<size>::ehdr_size);
 302   oehdr.put_e_phentsize(0);
 303   oehdr.put_e_phnum(0);
 304   oehdr.put_e_shentsize(elfcpp::Elf_sizes<size>::shdr_size);
 305   oehdr.put_e_shnum(5);
 306   oehdr.put_e_shstrndx(4);
 307
 308   *ppout += elfcpp::Elf_sizes<size>::ehdr_size;
 309 }
 310
 311 // Write out a section header.
 312
 313 template<int size, bool big_endian>
 314 void
 315 Binary_to_elf::write_section_header(
 316     const char* name,
 317     const Stringpool* shstrtab,
 318     elfcpp::SHT type,
 319     unsigned int flags,
 320     section_size_type offset,
 321     section_size_type section_size,
 322     unsigned int link,
 323     unsigned int info,
 324     unsigned int addralign,
 325     unsigned int entsize,
 326     unsigned char** ppout)
 327 {
 328   elfcpp::Shdr_write<size, big_endian> oshdr(*ppout);
 329
 330   oshdr.put_sh_name(*name == '\0' ? 0 : shstrtab->get_offset(name));
 331   oshdr.put_sh_type(type);
 332   oshdr.put_sh_flags(flags);
 333   oshdr.put_sh_addr(0);
 334   oshdr.put_sh_offset(offset);
 335   oshdr.put_sh_size(section_size);
 336   oshdr.put_sh_link(link);
 337   oshdr.put_sh_info(info);
 338   oshdr.put_sh_addralign(addralign);
 339   oshdr.put_sh_entsize(entsize);
 340
 341   *ppout += elfcpp::Elf_sizes<size>::shdr_size;
 342 }
 343
 344 // Write out a symbol.
 345
 346 template<int size, bool big_endian>
 347 void
 348 Binary_to_elf::write_symbol(
 349     const std::string& name,
 350     const Stringpool* strtab,
 351     section_size_type value,
 352     typename elfcpp::Elf_types<32>::Elf_WXword st_size,
 353     unsigned int shndx,
 354     unsigned char** ppout)
 355 {
 356   unsigned char* pout = *ppout;
 357
 358   elfcpp::Sym_write<size, big_endian> osym(pout);
 359   osym.put_st_name(name.empty() ? 0 : strtab->get_offset(name.c_str()));
 360   osym.put_st_value(value);
 361   osym.put_st_size(st_size);
 362   osym.put_st_info(name.empty() ? elfcpp::STB_LOCAL : elfcpp::STB_GLOBAL,
 363                    elfcpp::STT_NOTYPE);
 364   osym.put_st_other(elfcpp::STV_DEFAULT, 0);
 365   osym.put_st_shndx(shndx);
 366
 367   *ppout += elfcpp::Elf_sizes<size>::sym_size;
 368 }
 369
 370 } // End namespace gold.