gold/compressed_output.cc

   1 // compressed_output.cc -- manage compressed debug sections for gold
   2
   3 // Copyright 2007, 2008, 2010 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 #ifdef HAVE_ZLIB_H
  26 #include <zlib.h>
  27 #endif
  28
  29 #include "parameters.h"
  30 #include "options.h"
  31 #include "compressed_output.h"
  32
  33 namespace gold
  34 {
  35
  36 #ifdef HAVE_ZLIB_H
  37
  38 // Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns true
  39 // if it successfully compressed, false if it failed for any reason
  40 // (including not having zlib support in the library).  If it returns
  41 // true, it allocates memory for the compressed data using new, and
  42 // sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
  43 // It also writes a header before COMPRESSED_DATA: 4 bytes saying
  44 // "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian
  45 // order.
  46
  47 static bool
  48 zlib_compress(const unsigned char* uncompressed_data,
  49               unsigned long uncompressed_size,
  50               unsigned char** compressed_data,
  51               unsigned long* compressed_size)
  52 {
  53   const int header_size = 12;
  54   *compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
  55   *compressed_data = new unsigned char[*compressed_size + header_size];
  56
  57   int compress_level;
  58   if (parameters->options().optimize() >= 1)
  59     compress_level = 9;
  60   else
  61     compress_level = 1;
  62
  63   int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,
  64                      compressed_size,
  65                      reinterpret_cast<const Bytef*>(uncompressed_data),
  66                      uncompressed_size,
  67                      compress_level);
  68   if (rc == Z_OK)
  69     {
  70       memcpy(*compressed_data, "ZLIB", 4);
  71       elfcpp::Swap_unaligned<64, true>::writeval(*compressed_data + 4,
  72                                                  uncompressed_size);
  73       *compressed_size += header_size;
  74       return true;
  75     }
  76   else
  77     {
  78       delete[] *compressed_data;
  79       *compressed_data = NULL;
  80       return false;
  81     }
  82 }
  83
  84 // Decompress COMPRESSED_DATA of size COMPRESSED_SIZE, into a buffer
  85 // UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns TRUE if it
  86 // decompressed successfully, false if it failed.  The buffer, of
  87 // appropriate size, is provided by the caller, and is typically part
  88 // of the memory-mapped output file.
  89
  90 static bool
  91 zlib_decompress(const unsigned char* compressed_data,
  92                 unsigned long compressed_size,
  93                 unsigned char* uncompressed_data,
  94                 unsigned long uncompressed_size)
  95 {
  96   z_stream strm;
  97   int rc;
  98
  99   /* It is possible the section consists of several compressed
 100      buffers concatenated together, so we uncompress in a loop.  */
 101   strm.zalloc = NULL;
 102   strm.zfree = NULL;
 103   strm.opaque = NULL;
 104   strm.avail_in = compressed_size;
 105   strm.next_in = const_cast<Bytef*>(compressed_data);
 106   strm.avail_out = uncompressed_size;
 107
 108   rc = inflateInit(&strm);
 109   while (strm.avail_in > 0)
 110     {
 111       if (rc != Z_OK)
 112         return false;
 113       strm.next_out = ((Bytef*) uncompressed_data
 114                        + (uncompressed_size - strm.avail_out));
 115       rc = inflate(&strm, Z_FINISH);
 116       if (rc != Z_STREAM_END)
 117         return false;
 118       rc = inflateReset(&strm);
 119     }
 120   rc = inflateEnd(&strm);
 121   if (rc != Z_OK || strm.avail_out != 0)
 122     return false;
 123
 124   return true;
 125 }
 126
 127 #else // !defined(HAVE_ZLIB_H)
 128
 129 static bool
 130 zlib_compress(const unsigned char*, unsigned long,
 131               unsigned char**, unsigned long*)
 132 {
 133   return false;
 134 }
 135
 136 static bool
 137 zlib_decompress(const unsigned char*, unsigned long,
 138                 unsigned char*, unsigned long)
 139 {
 140   return false;
 141 }
 142
 143 #endif // !defined(HAVE_ZLIB_H)
 144
 145 // Read the compression header of a compressed debug section and return
 146 // the uncompressed size.
 147
 148 uint64_t
 149 get_uncompressed_size(const unsigned char* compressed_data,
 150                       section_size_type compressed_size)
 151 {
 152   const unsigned int zlib_header_size = 12;
 153
 154   /* Verify the compression header.  Currently, we support only zlib
 155      compression, so it should be "ZLIB" followed by the uncompressed
 156      section size, 8 bytes in big-endian order.  */
 157   if (compressed_size >= zlib_header_size
 158       && strncmp(reinterpret_cast<const char*>(compressed_data),
 159                  "ZLIB", 4) == 0)
 160     return elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 161   return -1ULL;
 162 }
 163
 164 // Decompress a compressed debug section directly into the output file.
 165
 166 bool
 167 decompress_input_section(const unsigned char* compressed_data,
 168                          unsigned long compressed_size,
 169                          unsigned char* uncompressed_data,
 170                          unsigned long uncompressed_size)
 171 {
 172   const unsigned int zlib_header_size = 12;
 173
 174   /* Verify the compression header.  Currently, we support only zlib
 175      compression, so it should be "ZLIB" followed by the uncompressed
 176      section size, 8 bytes in big-endian order.  */
 177   if (compressed_size >= zlib_header_size
 178       && strncmp(reinterpret_cast<const char*>(compressed_data),
 179                  "ZLIB", 4) == 0)
 180     {
 181       unsigned long uncompressed_size_check =
 182           elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 183       gold_assert(uncompressed_size_check == uncompressed_size);
 184       return zlib_decompress(compressed_data + zlib_header_size,
 185                              compressed_size - zlib_header_size,
 186                              uncompressed_data,
 187                              uncompressed_size);
 188     }
 189   return false;
 190 }
 191
 192 // Class Output_compressed_section.
 193
 194 // Set the final data size of a compressed section.  This is where
 195 // we actually compress the section data.
 196
 197 void
 198 Output_compressed_section::set_final_data_size()
 199 {
 200   off_t uncompressed_size = this->postprocessing_buffer_size();
 201
 202   // (Try to) compress the data.
 203   unsigned long compressed_size;
 204   unsigned char* uncompressed_data = this->postprocessing_buffer();
 205
 206   // At this point the contents of all regular input sections will
 207   // have been copied into the postprocessing buffer, and relocations
 208   // will have been applied.  Now we need to copy in the contents of
 209   // anything other than a regular input section.
 210   this->write_to_postprocessing_buffer();
 211
 212   bool success = false;
 213   if (strcmp(this->options_->compress_debug_sections(), "zlib") == 0)
 214     success = zlib_compress(uncompressed_data, uncompressed_size,
 215                             &this->data_, &compressed_size);
 216   if (success)
 217     {
 218       // This converts .debug_foo to .zdebug_foo
 219       this->new_section_name_ = std::string(".z") + (this->name() + 1);
 220       this->set_name(this->new_section_name_.c_str());
 221       this->set_data_size(compressed_size);
 222     }
 223   else
 224     {
 225       gold_warning(_("not compressing section data: zlib error"));
 226       gold_assert(this->data_ == NULL);
 227       this->set_data_size(uncompressed_size);
 228     }
 229 }
 230
 231 // Write out a compressed section.  If we couldn't compress, we just
 232 // write it out as normal, uncompressed data.
 233
 234 void
 235 Output_compressed_section::do_write(Output_file* of)
 236 {
 237   off_t offset = this->offset();
 238   off_t data_size = this->data_size();
 239   unsigned char* view = of->get_output_view(offset, data_size);
 240   if (this->data_ == NULL)
 241     memcpy(view, this->postprocessing_buffer(), data_size);
 242   else
 243     memcpy(view, this->data_, data_size);
 244   of->write_output_view(offset, data_size, view);
 245 }
 246
 247 } // End namespace gold.