gold/compressed_output.cc

   1 // compressed_output.cc -- manage compressed debug sections for gold
   2
   3 // Copyright (C) 2007-2023 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 #ifdef HAVE_ZSTD
  26 #include <zstd.h>
  27 #endif
  28 #include "parameters.h"
  29 #include "options.h"
  30 #include "compressed_output.h"
  31
  32 namespace gold
  33 {
  34
  35 // Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns true
  36 // if it successfully compressed, false if it failed for any reason
  37 // (including not having zlib support in the library).  If it returns
  38 // true, it allocates memory for the compressed data using new, and
  39 // sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
  40 // It also writes a header before COMPRESSED_DATA: 4 bytes saying
  41 // "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian
  42 // order.
  43
  44 static bool
  45 zlib_compress(int header_size,
  46               const unsigned char* uncompressed_data,
  47               unsigned long uncompressed_size,
  48               unsigned char** compressed_data,
  49               unsigned long* compressed_size)
  50 {
  51   *compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
  52   *compressed_data = new unsigned char[*compressed_size + header_size];
  53
  54   int compress_level;
  55   if (parameters->options().optimize() >= 1)
  56     compress_level = 9;
  57   else
  58     compress_level = 1;
  59
  60   int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,
  61                      compressed_size,
  62                      reinterpret_cast<const Bytef*>(uncompressed_data),
  63                      uncompressed_size,
  64                      compress_level);
  65   if (rc == Z_OK)
  66     {
  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 #if HAVE_ZSTD
  79 static bool
  80 zstd_compress(int header_size, const unsigned char *uncompressed_data,
  81               unsigned long uncompressed_size,
  82               unsigned char **compressed_data, unsigned long *compressed_size)
  83 {
  84   size_t size = ZSTD_compressBound(uncompressed_size);
  85   *compressed_data = new unsigned char[size + header_size];
  86   size = ZSTD_compress(*compressed_data + header_size, size, uncompressed_data,
  87                        uncompressed_size, ZSTD_CLEVEL_DEFAULT);
  88   if (ZSTD_isError(size))
  89     {
  90       delete[] *compressed_data;
  91       return false;
  92     }
  93   *compressed_size = header_size + size;
  94   return true;
  95 }
  96 #endif
  97
  98 // Decompress COMPRESSED_DATA of size COMPRESSED_SIZE, into a buffer
  99 // UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns TRUE if it
 100 // decompressed successfully, false if it failed.  The buffer, of
 101 // appropriate size, is provided by the caller, and is typically part
 102 // of the memory-mapped output file.
 103
 104 static bool
 105 zlib_decompress(const unsigned char* compressed_data,
 106                 unsigned long compressed_size,
 107                 unsigned char* uncompressed_data,
 108                 unsigned long uncompressed_size)
 109 {
 110   z_stream strm;
 111   int rc;
 112
 113   /* It is possible the section consists of several compressed
 114      buffers concatenated together, so we uncompress in a loop.  */
 115   strm.zalloc = NULL;
 116   strm.zfree = NULL;
 117   strm.opaque = NULL;
 118   strm.avail_in = compressed_size;
 119   strm.next_in = const_cast<Bytef*>(compressed_data);
 120   strm.avail_out = uncompressed_size;
 121
 122   rc = inflateInit(&strm);
 123   while (strm.avail_in > 0)
 124     {
 125       if (rc != Z_OK)
 126         return false;
 127       strm.next_out = ((Bytef*) uncompressed_data
 128                        + (uncompressed_size - strm.avail_out));
 129       rc = inflate(&strm, Z_FINISH);
 130       if (rc != Z_STREAM_END)
 131         return false;
 132       rc = inflateReset(&strm);
 133     }
 134   rc = inflateEnd(&strm);
 135   if (rc != Z_OK || strm.avail_out != 0)
 136     return false;
 137
 138   return true;
 139 }
 140
 141 // Read the compression header of a compressed debug section and return
 142 // the uncompressed size.
 143
 144 uint64_t
 145 get_uncompressed_size(const unsigned char* compressed_data,
 146                       section_size_type compressed_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     return elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 157   return -1ULL;
 158 }
 159
 160 // Decompress a compressed debug section directly into the output file.
 161
 162 bool
 163 decompress_input_section(const unsigned char* compressed_data,
 164                          unsigned long compressed_size,
 165                          unsigned char* uncompressed_data,
 166                          unsigned long uncompressed_size,
 167                          int size,
 168                          bool big_endian,
 169                          elfcpp::Elf_Xword sh_flags)
 170 {
 171   if ((sh_flags & elfcpp::SHF_COMPRESSED) != 0)
 172     {
 173       unsigned int compression_header_size;
 174       unsigned int ch_type;
 175       if (size == 32)
 176         {
 177           compression_header_size = elfcpp::Elf_sizes<32>::chdr_size;
 178           if (big_endian)
 179             ch_type = elfcpp::Chdr<32, true> (compressed_data).get_ch_type();
 180           else
 181             ch_type = elfcpp::Chdr<32, false>(compressed_data).get_ch_type();
 182         }
 183       else if (size == 64)
 184         {
 185           compression_header_size = elfcpp::Elf_sizes<64>::chdr_size;
 186           if (big_endian)
 187             ch_type = elfcpp::Chdr<64, true>(compressed_data).get_ch_type();
 188           else
 189             ch_type = elfcpp::Chdr<64, false>(compressed_data).get_ch_type();
 190         }
 191       else
 192         gold_unreachable();
 193
 194 #ifdef HAVE_ZSTD
 195       if (ch_type == elfcpp::ELFCOMPRESS_ZSTD)
 196         return !ZSTD_isError(
 197             ZSTD_decompress(uncompressed_data, uncompressed_size,
 198                             compressed_data + compression_header_size,
 199                             compressed_size - compression_header_size));
 200 #endif
 201       if (ch_type == elfcpp::ELFCOMPRESS_ZLIB)
 202         return zlib_decompress(compressed_data + compression_header_size,
 203                                compressed_size - compression_header_size,
 204                                uncompressed_data, uncompressed_size);
 205       return false;
 206     }
 207
 208   const unsigned int zlib_header_size = 12;
 209
 210   /* Verify the compression header.  Currently, we support only zlib
 211      compression, so it should be "ZLIB" followed by the uncompressed
 212      section size, 8 bytes in big-endian order.  */
 213   if (compressed_size >= zlib_header_size
 214       && strncmp(reinterpret_cast<const char*>(compressed_data),
 215                  "ZLIB", 4) == 0)
 216     {
 217       unsigned long uncompressed_size_check =
 218           elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);
 219       gold_assert(uncompressed_size_check == uncompressed_size);
 220       return zlib_decompress(compressed_data + zlib_header_size,
 221                              compressed_size - zlib_header_size,
 222                              uncompressed_data,
 223                              uncompressed_size);
 224     }
 225   return false;
 226 }
 227
 228 // Class Output_compressed_section.
 229
 230 // Set the final data size of a compressed section.  This is where
 231 // we actually compress the section data.
 232
 233 void
 234 Output_compressed_section::set_final_data_size()
 235 {
 236   off_t uncompressed_size = this->postprocessing_buffer_size();
 237
 238   // (Try to) compress the data.
 239   unsigned long compressed_size;
 240   unsigned char* uncompressed_data = this->postprocessing_buffer();
 241
 242   // At this point the contents of all regular input sections will
 243   // have been copied into the postprocessing buffer, and relocations
 244   // will have been applied.  Now we need to copy in the contents of
 245   // anything other than a regular input section.
 246   this->write_to_postprocessing_buffer();
 247
 248   bool success = false;
 249   enum { none, gnu_zlib, gabi_zlib, zstd } compress;
 250   int compression_header_size = 12;
 251   const int size = parameters->target().get_size();
 252   if (strcmp(this->options_->compress_debug_sections(), "zlib-gnu") == 0)
 253     compress = gnu_zlib;
 254   else if (strcmp(this->options_->compress_debug_sections(), "none") == 0)
 255     compress = none;
 256   else
 257     {
 258       if (strcmp(this->options_->compress_debug_sections(), "zstd") == 0)
 259         compress = zstd;
 260       else
 261         compress = gabi_zlib;
 262       if (size == 32)
 263         compression_header_size = elfcpp::Elf_sizes<32>::chdr_size;
 264       else if (size == 64)
 265         compression_header_size = elfcpp::Elf_sizes<64>::chdr_size;
 266       else
 267         gold_unreachable();
 268     }
 269   if (compress == gnu_zlib || compress == gabi_zlib)
 270     success = zlib_compress(compression_header_size, uncompressed_data,
 271                             uncompressed_size, &this->data_,
 272                             &compressed_size);
 273 #if HAVE_ZSTD
 274   else if (compress == zstd)
 275     success = zstd_compress(compression_header_size, uncompressed_data,
 276                             uncompressed_size, &this->data_,
 277                             &compressed_size);
 278 #endif
 279   if (success)
 280     {
 281       elfcpp::Elf_Xword flags = this->flags();
 282       if (compress == gabi_zlib || compress == zstd)
 283         {
 284           // Set the SHF_COMPRESSED bit.
 285           flags |= elfcpp::SHF_COMPRESSED;
 286           const bool is_big_endian = parameters->target().is_big_endian();
 287           const unsigned int ch_type = compress == zstd
 288                                            ? elfcpp::ELFCOMPRESS_ZSTD
 289                                            : elfcpp::ELFCOMPRESS_ZLIB;
 290           uint64_t addralign = this->addralign ();
 291           if (size == 32)
 292             {
 293               if (is_big_endian)
 294                 {
 295                   elfcpp::Chdr_write<32, true> chdr(this->data_);
 296                   chdr.put_ch_type(ch_type);
 297                   chdr.put_ch_size(uncompressed_size);
 298                   chdr.put_ch_addralign(addralign);
 299                 }
 300               else
 301                 {
 302                   elfcpp::Chdr_write<32, false> chdr(this->data_);
 303                   chdr.put_ch_type(ch_type);
 304                   chdr.put_ch_size(uncompressed_size);
 305                   chdr.put_ch_addralign(addralign);
 306                 }
 307             }
 308           else if (size == 64)
 309             {
 310               if (is_big_endian)
 311                 {
 312                   elfcpp::Chdr_write<64, true> chdr(this->data_);
 313                   chdr.put_ch_type(ch_type);
 314                   chdr.put_ch_size(uncompressed_size);
 315                   chdr.put_ch_addralign(addralign);
 316                   // Clear the reserved field.
 317                   chdr.put_ch_reserved(0);
 318                 }
 319               else
 320                 {
 321                   elfcpp::Chdr_write<64, false> chdr(this->data_);
 322                   chdr.put_ch_type(ch_type);
 323                   chdr.put_ch_size(uncompressed_size);
 324                   chdr.put_ch_addralign(addralign);
 325                   // Clear the reserved field.
 326                   chdr.put_ch_reserved(0);
 327                 }
 328             }
 329           else
 330             gold_unreachable();
 331         }
 332       else
 333         {
 334           // Write out the zlib header.
 335           memcpy(this->data_, "ZLIB", 4);
 336           elfcpp::Swap_unaligned<64, true>::writeval(this->data_ + 4,
 337                                                      uncompressed_size);
 338           // This converts .debug_foo to .zdebug_foo
 339           this->new_section_name_ = std::string(".z") + (this->name() + 1);
 340           this->set_name(this->new_section_name_.c_str());
 341         }
 342       this->set_flags(flags);
 343       this->set_data_size(compressed_size);
 344     }
 345   else
 346     {
 347       gold_warning(_("not compressing section data: zlib error"));
 348       gold_assert(this->data_ == NULL);
 349       this->set_data_size(uncompressed_size);
 350     }
 351 }
 352
 353 // Write out a compressed section.  If we couldn't compress, we just
 354 // write it out as normal, uncompressed data.
 355
 356 void
 357 Output_compressed_section::do_write(Output_file* of)
 358 {
 359   off_t offset = this->offset();
 360   off_t data_size = this->data_size();
 361   unsigned char* view = of->get_output_view(offset, data_size);
 362   if (this->data_ == NULL)
 363     memcpy(view, this->postprocessing_buffer(), data_size);
 364   else
 365     memcpy(view, this->data_, data_size);
 366   of->write_output_view(offset, data_size, view);
 367 }
 368
 369 } // End namespace gold.