1// compressed_output.cc -- manage compressed debug sections for gold
2
3// Copyright (C) 2007-2017 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
29namespace 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
41static bool
42zlib_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
81static bool
82zlib_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
121uint64_t
122get_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
139bool
140decompress_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
217void
218Output_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		}
290	      else
291		{
292		  elfcpp::Chdr_write<64, false> chdr(this->data_);
293		  chdr.put_ch_type(elfcpp::ELFCOMPRESS_ZLIB);
294		  chdr.put_ch_size(uncompressed_size);
295		  chdr.put_ch_addralign(addralign);
296		}
297	    }
298	  else
299	    gold_unreachable();
300	}
301      else
302	{
303	  // Write out the zlib header.
304	  memcpy(this->data_, "ZLIB", 4);
305	  elfcpp::Swap_unaligned<64, true>::writeval(this->data_ + 4,
306						     uncompressed_size);
307	  // This converts .debug_foo to .zdebug_foo
308	  this->new_section_name_ = std::string(".z") + (this->name() + 1);
309	  this->set_name(this->new_section_name_.c_str());
310	}
311      this->set_flags(flags);
312      this->set_data_size(compressed_size);
313    }
314  else
315    {
316      gold_warning(_("not compressing section data: zlib error"));
317      gold_assert(this->data_ == NULL);
318      this->set_data_size(uncompressed_size);
319    }
320}
321
322// Write out a compressed section.  If we couldn't compress, we just
323// write it out as normal, uncompressed data.
324
325void
326Output_compressed_section::do_write(Output_file* of)
327{
328  off_t offset = this->offset();
329  off_t data_size = this->data_size();
330  unsigned char* view = of->get_output_view(offset, data_size);
331  if (this->data_ == NULL)
332    memcpy(view, this->postprocessing_buffer(), data_size);
333  else
334    memcpy(view, this->data_, data_size);
335  of->write_output_view(offset, data_size, view);
336}
337
338} // End namespace gold.
339