1 // compressed_output.cc -- manage compressed debug sections for gold
2
3 // Copyright (C) 2007-2024 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
zlib_compress(int header_size,const unsigned char * uncompressed_data,unsigned long uncompressed_size,unsigned char ** compressed_data,unsigned long * compressed_size)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
zstd_compress(int header_size,const unsigned char * uncompressed_data,unsigned long uncompressed_size,unsigned char ** compressed_data,unsigned long * compressed_size)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
zlib_decompress(const unsigned char * compressed_data,unsigned long compressed_size,unsigned char * uncompressed_data,unsigned long uncompressed_size)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
get_uncompressed_size(const unsigned char * compressed_data,section_size_type compressed_size)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
decompress_input_section(const unsigned char * compressed_data,unsigned long compressed_size,unsigned char * uncompressed_data,unsigned long uncompressed_size,int size,bool big_endian,elfcpp::Elf_Xword sh_flags)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
set_final_data_size()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
do_write(Output_file * of)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.
370