1 // compressed_output.cc -- manage compressed debug sections for gold
2 
3 // Copyright (C) 2007-2016 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 		}
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 
325 void
326 Output_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