gold/compressed_output.cc

   1 // compressed_output.cc -- manage compressed debug sections for gold
   2
   3 // Copyright (C) 2007-2015 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(const unsigned char* uncompressed_data,
  43               unsigned long uncompressed_size,
  44               unsigned char** compressed_data,
  45               unsigned long* compressed_size)
  46 {
  47   const int header_size = 12;
  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       memcpy(*compressed_data, "ZLIB", 4);
  65       elfcpp::Swap_unaligned<64, true>::writeval(*compressed_data + 4,
  66                                                  uncompressed_size);
  67       *compressed_size += header_size;
  68       return true;
  69     }
  70   else
  71     {
  72       delete[] *compressed_data;
  73       *compressed_data = NULL;
  74       return false;
  75     }
  76 }
  77
  78 // Decompress COMPRESSED_DATA of size COMPRESSED_SIZE, into a buffer
  79 // UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns TRUE if it
  80 // decompressed successfully, false if it failed.  The buffer, of
  81 // appropriate size, is provided by the caller, and is typically part
  82 // of the memory-mapped output file.
  83
  84 static bool
  85 zlib_decompress(const unsigned char* compressed_data,
  86                 unsigned long compressed_size,
  87                 unsigned char* uncompressed_data,
  88                 unsigned long uncompressed_size)
  89 {
  90   z_stream strm;
  91   int rc;
  92
  93   /* It is possible the section consists of several compressed
  94      buffers concatenated together, so we uncompress in a loop.  */
  95   strm.zalloc = NULL;
  96   strm.zfree = NULL;
  97   strm.opaque = NULL;
  98   strm.avail_in = compressed_size;
  99   strm.next_in = const_cast<Bytef*>(compressed_data);
 100   strm.avail_out = uncompressed_size;
 101
 102   rc = inflateInit(&strm);
 103   while (strm.avail_in > 0)
 104     {
 105       if (rc != Z_OK)
 106         return false;
 107       strm.next_out = ((Bytef*) uncompressed_data
 108                        + (uncompressed_size - strm.avail_out));
 109       rc = inflate(&strm, Z_FINISH);
 110       if (rc != Z_STREAM_END)
 111         return false;
 112       rc = inflateReset(&strm);
 113     }
 114   rc = inflateEnd(&strm);
 115   if (rc != Z_OK || strm.avail_out != 0)
 116     return false;
 117
 118   return true;
 119 }
 120
 121 // Read the compression header of a compressed debug section and return
 122 // the uncompressed size.
 123
 124 uint64_t
 125 get_uncompressed_size(const unsigned char* compressed_data,
 126                       section_size_type compressed_size)
 127 {
 128   const unsigned int zlib_header_size = 12;
 129
 130   /* Verify the compression header.  Currently, we support only zlib
 131      compression, so it should be "ZLIB" followed by the uncompressed
 132      section size, 8 bytes in big-endian order.  */
 133   if (compressed_size >= zlib_header_size
 134       && strncmp(reinterpret_cast<const char*>(compressed_data),
 135                  "ZLIB", 4) == 0)
 136     return elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 137   return -1ULL;
 138 }
 139
 140 // Decompress a compressed debug section directly into the output file.
 141
 142 bool
 143 decompress_input_section(const unsigned char* compressed_data,
 144                          unsigned long compressed_size,
 145                          unsigned char* uncompressed_data,
 146                          unsigned long uncompressed_size)
 147 {
 148   const unsigned int zlib_header_size = 12;
 149
 150   /* Verify the compression header.  Currently, we support only zlib
 151      compression, so it should be "ZLIB" followed by the uncompressed
 152      section size, 8 bytes in big-endian order.  */
 153   if (compressed_size >= zlib_header_size
 154       && strncmp(reinterpret_cast<const char*>(compressed_data),
 155                  "ZLIB", 4) == 0)
 156     {
 157       unsigned long uncompressed_size_check =
 158           elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 159       gold_assert(uncompressed_size_check == uncompressed_size);
 160       return zlib_decompress(compressed_data + zlib_header_size,
 161                              compressed_size - zlib_header_size,
 162                              uncompressed_data,
 163                              uncompressed_size);
 164     }
 165   return false;
 166 }
 167
 168 // Class Output_compressed_section.
 169
 170 // Set the final data size of a compressed section.  This is where
 171 // we actually compress the section data.
 172
 173 void
 174 Output_compressed_section::set_final_data_size()
 175 {
 176   off_t uncompressed_size = this->postprocessing_buffer_size();
 177
 178   // (Try to) compress the data.
 179   unsigned long compressed_size;
 180   unsigned char* uncompressed_data = this->postprocessing_buffer();
 181
 182   // At this point the contents of all regular input sections will
 183   // have been copied into the postprocessing buffer, and relocations
 184   // will have been applied.  Now we need to copy in the contents of
 185   // anything other than a regular input section.
 186   this->write_to_postprocessing_buffer();
 187
 188   bool success = false;
 189   if (strcmp(this->options_->compress_debug_sections(), "zlib") == 0)
 190     success = zlib_compress(uncompressed_data, uncompressed_size,
 191                             &this->data_, &compressed_size);
 192   if (success)
 193     {
 194       // This converts .debug_foo to .zdebug_foo
 195       this->new_section_name_ = std::string(".z") + (this->name() + 1);
 196       this->set_name(this->new_section_name_.c_str());
 197       this->set_data_size(compressed_size);
 198     }
 199   else
 200     {
 201       gold_warning(_("not compressing section data: zlib error"));
 202       gold_assert(this->data_ == NULL);
 203       this->set_data_size(uncompressed_size);
 204     }
 205 }
 206
 207 // Write out a compressed section.  If we couldn't compress, we just
 208 // write it out as normal, uncompressed data.
 209
 210 void
 211 Output_compressed_section::do_write(Output_file* of)
 212 {
 213   off_t offset = this->offset();
 214   off_t data_size = this->data_size();
 215   unsigned char* view = of->get_output_view(offset, data_size);
 216   if (this->data_ == NULL)
 217     memcpy(view, this->postprocessing_buffer(), data_size);
 218   else
 219     memcpy(view, this->data_, data_size);
 220   of->write_output_view(offset, data_size, view);
 221 }
 222
 223 } // End namespace gold.