gold/compressed_output.cc

   1 // compressed_output.cc -- manage compressed debug sections for gold
   2
   3 // Copyright (C) 2007-2020 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 #include <zlib.h>
  25 #include "parameters.h"
  26 #include "options.h"
  27 #include "compressed_output.h"
  28
  29 namespace gold
  30 {
  31
  32 // Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns true
  33 // if it successfully compressed, false if it failed for any reason
  34 // (including not having zlib support in the library).  If it returns
  35 // true, it allocates memory for the compressed data using new, and
  36 // sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
  37 // It also writes a header before COMPRESSED_DATA: 4 bytes saying
  38 // "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian
  39 // order.
  40
  41 static bool
  42 zlib_compress(int header_size,
  43               const unsigned char* uncompressed_data,
  44               unsigned long uncompressed_size,
  45               unsigned char** compressed_data,
  46               unsigned long* compressed_size)
  47 {
  48   *compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
  49   *compressed_data = new unsigned char[*compressed_size + header_size];
  50
  51   int compress_level;
  52   if (parameters->options().optimize() >= 1)
  53     compress_level = 9;
  54   else
  55     compress_level = 1;
  56
  57   int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,
  58                      compressed_size,
  59                      reinterpret_cast<const Bytef*>(uncompressed_data),
  60                      uncompressed_size,
  61                      compress_level);
  62   if (rc == Z_OK)
  63     {
  64       *compressed_size += header_size;
  65       return true;
  66     }
  67   else
  68     {
  69       delete[] *compressed_data;
  70       *compressed_data = NULL;
  71       return false;
  72     }
  73 }
  74
  75 // Decompress COMPRESSED_DATA of size COMPRESSED_SIZE, into a buffer
  76 // UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns TRUE if it
  77 // decompressed successfully, false if it failed.  The buffer, of
  78 // appropriate size, is provided by the caller, and is typically part
  79 // of the memory-mapped output file.
  80
  81 static bool
  82 zlib_decompress(const unsigned char* compressed_data,
  83                 unsigned long compressed_size,
  84                 unsigned char* uncompressed_data,
  85                 unsigned long uncompressed_size)
  86 {
  87   z_stream strm;
  88   int rc;
  89
  90   /* It is possible the section consists of several compressed
  91      buffers concatenated together, so we uncompress in a loop.  */
  92   strm.zalloc = NULL;
  93   strm.zfree = NULL;
  94   strm.opaque = NULL;
  95   strm.avail_in = compressed_size;
  96   strm.next_in = const_cast<Bytef*>(compressed_data);
  97   strm.avail_out = uncompressed_size;
  98
  99   rc = inflateInit(&strm);
 100   while (strm.avail_in > 0)
 101     {
 102       if (rc != Z_OK)
 103         return false;
 104       strm.next_out = ((Bytef*) uncompressed_data
 105                        + (uncompressed_size - strm.avail_out));
 106       rc = inflate(&strm, Z_FINISH);
 107       if (rc != Z_STREAM_END)
 108         return false;
 109       rc = inflateReset(&strm);
 110     }
 111   rc = inflateEnd(&strm);
 112   if (rc != Z_OK || strm.avail_out != 0)
 113     return false;
 114
 115   return true;
 116 }
 117
 118 // Read the compression header of a compressed debug section and return
 119 // the uncompressed size.
 120
 121 uint64_t
 122 get_uncompressed_size(const unsigned char* compressed_data,
 123                       section_size_type compressed_size)
 124 {
 125   const unsigned int zlib_header_size = 12;
 126
 127   /* Verify the compression header.  Currently, we support only zlib
 128      compression, so it should be "ZLIB" followed by the uncompressed
 129      section size, 8 bytes in big-endian order.  */
 130   if (compressed_size >= zlib_header_size
 131       && strncmp(reinterpret_cast<const char*>(compressed_data),
 132                  "ZLIB", 4) == 0)
 133     return elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 134   return -1ULL;
 135 }
 136
 137 // Decompress a compressed debug section directly into the output file.
 138
 139 bool
 140 decompress_input_section(const unsigned char* compressed_data,
 141                          unsigned long compressed_size,
 142                          unsigned char* uncompressed_data,
 143                          unsigned long uncompressed_size,
 144                          int size,
 145                          bool big_endian,
 146                          elfcpp::Elf_Xword sh_flags)
 147 {
 148   if ((sh_flags & elfcpp::SHF_COMPRESSED) != 0)
 149     {
 150       unsigned int compression_header_size;
 151       if (size == 32)
 152         {
 153           compression_header_size = elfcpp::Elf_sizes<32>::chdr_size;
 154           if (big_endian)
 155             {
 156               elfcpp::Chdr<32, true> chdr(compressed_data);
 157               if (chdr.get_ch_type() != elfcpp::ELFCOMPRESS_ZLIB)
 158                 return false;
 159             }
 160           else
 161             {
 162               elfcpp::Chdr<32, false> chdr(compressed_data);
 163               if (chdr.get_ch_type() != elfcpp::ELFCOMPRESS_ZLIB)
 164                 return false;
 165             }
 166         }
 167       else if (size == 64)
 168         {
 169           compression_header_size = elfcpp::Elf_sizes<64>::chdr_size;
 170           if (big_endian)
 171             {
 172               elfcpp::Chdr<64, true> chdr(compressed_data);
 173               if (chdr.get_ch_type() != elfcpp::ELFCOMPRESS_ZLIB)
 174                 return false;
 175             }
 176           else
 177             {
 178               elfcpp::Chdr<64, false> chdr(compressed_data);
 179               if (chdr.get_ch_type() != elfcpp::ELFCOMPRESS_ZLIB)
 180                 return false;
 181             }
 182         }
 183       else
 184         gold_unreachable();
 185
 186       return zlib_decompress(compressed_data + compression_header_size,
 187                              compressed_size - compression_header_size,
 188                              uncompressed_data,
 189                              uncompressed_size);
 190     }
 191
 192   const unsigned int zlib_header_size = 12;
 193
 194   /* Verify the compression header.  Currently, we support only zlib
 195      compression, so it should be "ZLIB" followed by the uncompressed
 196      section size, 8 bytes in big-endian order.  */
 197   if (compressed_size >= zlib_header_size
 198       && strncmp(reinterpret_cast<const char*>(compressed_data),
 199                  "ZLIB", 4) == 0)
 200     {
 201       unsigned long uncompressed_size_check =
 202           elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 203       gold_assert(uncompressed_size_check == uncompressed_size);
 204       return zlib_decompress(compressed_data + zlib_header_size,
 205                              compressed_size - zlib_header_size,
 206                              uncompressed_data,
 207                              uncompressed_size);
 208     }
 209   return false;
 210 }
 211
 212 // Class Output_compressed_section.
 213
 214 // Set the final data size of a compressed section.  This is where
 215 // we actually compress the section data.
 216
 217 void
 218 Output_compressed_section::set_final_data_size()
 219 {
 220   off_t uncompressed_size = this->postprocessing_buffer_size();
 221
 222   // (Try to) compress the data.
 223   unsigned long compressed_size;
 224   unsigned char* uncompressed_data = this->postprocessing_buffer();
 225
 226   // At this point the contents of all regular input sections will
 227   // have been copied into the postprocessing buffer, and relocations
 228   // will have been applied.  Now we need to copy in the contents of
 229   // anything other than a regular input section.
 230   this->write_to_postprocessing_buffer();
 231
 232   bool success = false;
 233   enum { none, gnu_zlib, gabi_zlib } compress;
 234   int compression_header_size = 12;
 235   const int size = parameters->target().get_size();
 236   if (strcmp(this->options_->compress_debug_sections(), "zlib-gnu") == 0)
 237     compress = gnu_zlib;
 238   else if (strcmp(this->options_->compress_debug_sections(), "zlib-gabi") == 0
 239            || strcmp(this->options_->compress_debug_sections(), "zlib") == 0)
 240     {
 241       compress = gabi_zlib;
 242       if (size == 32)
 243         compression_header_size = elfcpp::Elf_sizes<32>::chdr_size;
 244       else if (size == 64)
 245         compression_header_size = elfcpp::Elf_sizes<64>::chdr_size;
 246       else
 247         gold_unreachable();
 248     }
 249   else
 250     compress = none;
 251   if (compress != none)
 252     success = zlib_compress(compression_header_size, uncompressed_data,
 253                             uncompressed_size, &this->data_,
 254                             &compressed_size);
 255   if (success)
 256     {
 257       elfcpp::Elf_Xword flags = this->flags();
 258       if (compress == gabi_zlib)
 259         {
 260           // Set the SHF_COMPRESSED bit.
 261           flags |= elfcpp::SHF_COMPRESSED;
 262           const bool is_big_endian = parameters->target().is_big_endian();
 263           uint64_t addralign = this->addralign();
 264           if (size == 32)
 265             {
 266               if (is_big_endian)
 267                 {
 268                   elfcpp::Chdr_write<32, true> chdr(this->data_);
 269                   chdr.put_ch_type(elfcpp::ELFCOMPRESS_ZLIB);
 270                   chdr.put_ch_size(uncompressed_size);
 271                   chdr.put_ch_addralign(addralign);
 272                 }
 273               else
 274                 {
 275                   elfcpp::Chdr_write<32, false> chdr(this->data_);
 276                   chdr.put_ch_type(elfcpp::ELFCOMPRESS_ZLIB);
 277                   chdr.put_ch_size(uncompressed_size);
 278                   chdr.put_ch_addralign(addralign);
 279                 }
 280             }
 281           else if (size == 64)
 282             {
 283               if (is_big_endian)
 284                 {
 285                   elfcpp::Chdr_write<64, true> chdr(this->data_);
 286                   chdr.put_ch_type(elfcpp::ELFCOMPRESS_ZLIB);
 287                   chdr.put_ch_size(uncompressed_size);
 288                   chdr.put_ch_addralign(addralign);
 289                   // Clear the reserved field.
 290                   chdr.put_ch_reserved(0);
 291                 }
 292               else
 293                 {
 294                   elfcpp::Chdr_write<64, false> chdr(this->data_);
 295                   chdr.put_ch_type(elfcpp::ELFCOMPRESS_ZLIB);
 296                   chdr.put_ch_size(uncompressed_size);
 297                   chdr.put_ch_addralign(addralign);
 298                   // Clear the reserved field.
 299                   chdr.put_ch_reserved(0);
 300                 }
 301             }
 302           else
 303             gold_unreachable();
 304         }
 305       else
 306         {
 307           // Write out the zlib header.
 308           memcpy(this->data_, "ZLIB", 4);
 309           elfcpp::Swap_unaligned<64, true>::writeval(this->data_ + 4,
 310                                                      uncompressed_size);
 311           // This converts .debug_foo to .zdebug_foo
 312           this->new_section_name_ = std::string(".z") + (this->name() + 1);
 313           this->set_name(this->new_section_name_.c_str());
 314         }
 315       this->set_flags(flags);
 316       this->set_data_size(compressed_size);
 317     }
 318   else
 319     {
 320       gold_warning(_("not compressing section data: zlib error"));
 321       gold_assert(this->data_ == NULL);
 322       this->set_data_size(uncompressed_size);
 323     }
 324 }
 325
 326 // Write out a compressed section.  If we couldn't compress, we just
 327 // write it out as normal, uncompressed data.
 328
 329 void
 330 Output_compressed_section::do_write(Output_file* of)
 331 {
 332   off_t offset = this->offset();
 333   off_t data_size = this->data_size();
 334   unsigned char* view = of->get_output_view(offset, data_size);
 335   if (this->data_ == NULL)
 336     memcpy(view, this->postprocessing_buffer(), data_size);
 337   else
 338     memcpy(view, this->data_, data_size);
 339   of->write_output_view(offset, data_size, view);
 340 }
 341
 342 } // End namespace gold.