1 // reduced_debug_output.cc -- output reduced debugging information to save space
3 // Copyright 2008 Free Software Foundation, Inc.
4 // Written by Caleb Howe <cshowe@google.com>.
6 // This file is part of gold.
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.
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.
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.
25 #include "parameters.h"
28 #include "dwarf_reader.h"
29 #include "reduced_debug_output.h"
30 #include "int_encoding.h"
37 // Given a pointer to the beginning of a die and the beginning of the associated
38 // abbreviation fills in die_end with the end of the information entry. If
39 // successful returns true. Get_die_end also takes a pointer to the end of the
40 // buffer containing the die. If die_end would be beyond the end of the
41 // buffer, or if an unsupported dwarf form is encountered returns false.
43 Output_reduced_debug_info_section::get_die_end(
44 unsigned char* die
, unsigned char* abbrev
, unsigned char** die_end
,
45 unsigned char* buffer_end
, int address_size
, bool is64
)
51 uint64_t attribute
= read_unsigned_LEB_128(abbrev
, &LEB_size
);
53 elfcpp::DW_FORM form
=
54 static_cast<elfcpp::DW_FORM
>(read_unsigned_LEB_128(abbrev
,
57 if (!(attribute
|| form
))
59 if (die
>= buffer_end
)
63 case elfcpp::DW_FORM_null
:
65 case elfcpp::DW_FORM_strp
:
68 case elfcpp::DW_FORM_addr
:
69 case elfcpp::DW_FORM_ref_addr
:
72 case elfcpp::DW_FORM_block1
:
76 case elfcpp::DW_FORM_block2
:
79 block_size
= read_from_pointer
<16>(&die
);
83 case elfcpp::DW_FORM_block4
:
86 block_size
= read_from_pointer
<32>(&die
);
90 case elfcpp::DW_FORM_block
:
91 LEB_decoded
= read_unsigned_LEB_128(die
, &LEB_size
);
92 die
+= (LEB_decoded
+ LEB_size
);
94 case elfcpp::DW_FORM_data1
:
95 case elfcpp::DW_FORM_ref1
:
96 case elfcpp::DW_FORM_flag
:
99 case elfcpp::DW_FORM_data2
:
100 case elfcpp::DW_FORM_ref2
:
103 case elfcpp::DW_FORM_data4
:
104 case elfcpp::DW_FORM_ref4
:
107 case elfcpp::DW_FORM_data8
:
108 case elfcpp::DW_FORM_ref8
:
111 case elfcpp::DW_FORM_ref_udata
:
112 case elfcpp::DW_FORM_udata
:
113 read_unsigned_LEB_128(die
, &LEB_size
);
116 case elfcpp::DW_FORM_string
:
118 size_t length
= strlen(reinterpret_cast<char*>(die
));
122 case elfcpp::DW_FORM_sdata
:
123 case elfcpp::DW_FORM_indirect
:
132 Output_reduced_debug_abbrev_section::set_final_data_size()
134 if (this->sized_
|| this->failed_
)
137 uint64_t abbrev_number
;
139 unsigned char* abbrev_data
= this->postprocessing_buffer();
140 unsigned char* abbrev_end
= this->postprocessing_buffer() +
141 this->postprocessing_buffer_size();
142 this->write_to_postprocessing_buffer();
143 while(abbrev_data
< abbrev_end
)
145 uint64_t abbrev_offset
= abbrev_data
- this->postprocessing_buffer();
146 while((abbrev_number
= read_unsigned_LEB_128(abbrev_data
, &LEB_size
)))
148 if (abbrev_data
>= abbrev_end
)
150 failed("Debug abbreviations extend beyond .debug_abbrev "
151 "section; failed to reduce debug abbreviations");
154 abbrev_data
+= LEB_size
;
156 // Together with the abbreviation number these fields make up
157 // the header for each abbreviation
158 uint64_t abbrev_type
= read_unsigned_LEB_128(abbrev_data
, &LEB_size
);
159 abbrev_data
+= LEB_size
;
161 // This would ordinarily be the has_children field of the
162 // abbreviation. But it's going to be false after reducting the
163 // information, so there's no point in storing it
166 // Read to the end of the current abbreviation
167 // This is indicated by two zero unsigned LEBs in a row. We don't
168 // need to parse the data yet, so we just scan through the data
169 // looking for two consecutive 0 bytes indicating the end of the
171 unsigned char* current_abbrev
;
172 for (current_abbrev
= abbrev_data
;
173 current_abbrev
[0] || current_abbrev
[1];
176 if (current_abbrev
>= abbrev_end
)
178 this->failed(_("Debug abbreviations extend beyond "
179 ".debug_abbrev section; failed to reduce "
180 "debug abbreviations"));
184 // Account for the two nulls and advance to the start of the
185 // next abbreviation.
188 // We're eliminating every entry except for compile units, so we
189 // only need to store abbreviations that describe them
190 if (abbrev_type
== elfcpp::DW_TAG_compile_unit
)
192 write_unsigned_LEB_128(&this->data_
, ++this->abbrev_count_
);
193 write_unsigned_LEB_128(&this->data_
, abbrev_type
);
194 // has_children is false for all entries
195 this->data_
.push_back(0);
196 this->abbrev_mapping_
[std::make_pair(abbrev_offset
,
198 std::make_pair(abbrev_count_
, this->data_
.size());
199 this->data_
.insert(this->data_
.end(), abbrev_data
,
202 abbrev_data
= current_abbrev
;
204 gold_assert(LEB_size
== 1);
205 abbrev_data
+= LEB_size
;
207 // Null terminate the list of abbreviations
208 this->data_
.push_back(0);
209 this->set_data_size(data_
.size());
214 Output_reduced_debug_abbrev_section::do_write(Output_file
* of
)
216 off_t offset
= this->offset();
217 off_t data_size
= this->data_size();
218 unsigned char* view
= of
->get_output_view(offset
, data_size
);
220 memcpy(view
, this->postprocessing_buffer(),
221 this->postprocessing_buffer_size());
223 memcpy(view
, &this->data_
.front(), data_size
);
224 of
->write_output_view(offset
, data_size
, view
);
227 // Locates the abbreviation with abbreviation_number abbrev_number in the
228 // abbreviation table at offset abbrev_offset. abbrev_number is updated with
229 // its new abbreviation number and a pointer to the beginning of the
230 // abbreviation is returned.
232 Output_reduced_debug_abbrev_section::get_new_abbrev(
233 uint64_t* abbrev_number
, uint64_t abbrev_offset
)
235 set_final_data_size();
236 std::pair
<uint64_t, uint64_t> abbrev_info
=
237 this->abbrev_mapping_
[std::make_pair(abbrev_offset
, *abbrev_number
)];
238 *abbrev_number
= abbrev_info
.first
;
239 return &this->data_
[abbrev_info
.second
];
242 void Output_reduced_debug_info_section::set_final_data_size()
246 unsigned char* debug_info
= this->postprocessing_buffer();
247 unsigned char* debug_info_end
= (this->postprocessing_buffer()
248 + this->postprocessing_buffer_size());
249 unsigned char* next_compile_unit
;
250 this->write_to_postprocessing_buffer();
252 while (debug_info
< debug_info_end
)
254 uint32_t compile_unit_start
= read_from_pointer
<32>(&debug_info
);
255 // The first 4 bytes of each compile unit determine whether or
256 // not we're using dwarf32 or dwarf64. This is not necessarily
257 // related to whether the binary is 32 or 64 bits.
258 if (compile_unit_start
== 0xFFFFFFFF)
260 // Technically the size can be up to 96 bits. Rather than handle
261 // 96/128 bit integers we just truncate the size at 64 bits.
262 if (0 != read_from_pointer
<32>(&debug_info
))
264 this->failed(_("Extremely large compile unit in debug info; "
265 "failed to reduce debug info"));
268 const int dwarf64_header_size
= sizeof(uint64_t) + sizeof(uint16_t) +
269 sizeof(uint64_t) + sizeof(uint8_t);
270 if (debug_info
+ dwarf64_header_size
>= debug_info_end
)
272 this->failed(_("Debug info extends beyond .debug_info section;"
273 "failed to reduce debug info"));
277 uint64_t compile_unit_size
= read_from_pointer
<64>(&debug_info
);
278 next_compile_unit
= debug_info
+ compile_unit_size
;
279 uint16_t version
= read_from_pointer
<16>(&debug_info
);
280 uint64_t abbrev_offset
= read_from_pointer
<64>(&debug_info
);
281 uint8_t address_size
= read_from_pointer
<8>(&debug_info
);
283 uint64_t abbreviation_number
= read_unsigned_LEB_128(debug_info
,
285 debug_info
+= LEB_size
;
286 unsigned char* die_abbrev
= this->associated_abbrev_
->get_new_abbrev(
287 &abbreviation_number
, abbrev_offset
);
288 unsigned char* die_end
;
289 if (!this->get_die_end(debug_info
, die_abbrev
, &die_end
,
290 debug_info_end
, address_size
, true))
292 this->failed(_("Invalid DIE in debug info; "
293 "failed to reduce debug info"));
297 insert_into_vector
<32>(&this->data_
, 0xFFFFFFFF);
298 insert_into_vector
<32>(&this->data_
, 0);
299 insert_into_vector
<64>(
301 (11 + get_length_as_unsigned_LEB_128(abbreviation_number
)
302 + die_end
- debug_info
));
303 insert_into_vector
<16>(&this->data_
, version
);
304 insert_into_vector
<64>(&this->data_
, 0);
305 insert_into_vector
<8>(&this->data_
, address_size
);
306 write_unsigned_LEB_128(&this->data_
, abbreviation_number
);
307 this->data_
.insert(this->data_
.end(), debug_info
, die_end
);
311 const int dwarf32_header_size
=
312 sizeof(uint16_t) + sizeof(uint32_t) + sizeof(uint8_t);
313 if (debug_info
+ dwarf32_header_size
>= debug_info_end
)
315 this->failed(_("Debug info extends beyond .debug_info section; "
316 "failed to reduce debug info"));
319 uint32_t compile_unit_size
= compile_unit_start
;
320 next_compile_unit
= debug_info
+ compile_unit_size
;
321 uint16_t version
= read_from_pointer
<16>(&debug_info
);
322 uint32_t abbrev_offset
= read_from_pointer
<32>(&debug_info
);
323 uint8_t address_size
= read_from_pointer
<8>(&debug_info
);
325 uint64_t abbreviation_number
= read_unsigned_LEB_128(debug_info
,
327 debug_info
+= LEB_size
;
328 unsigned char* die_abbrev
= this->associated_abbrev_
->get_new_abbrev(
329 &abbreviation_number
, abbrev_offset
);
330 unsigned char* die_end
;
331 if (!this->get_die_end(debug_info
, die_abbrev
, &die_end
,
332 debug_info_end
, address_size
, false))
334 this->failed(_("Invalid DIE in debug info; "
335 "failed to reduce debug info"));
339 insert_into_vector
<32>(
341 (7 + get_length_as_unsigned_LEB_128(abbreviation_number
)
342 + die_end
- debug_info
));
343 insert_into_vector
<16>(&this->data_
, version
);
344 insert_into_vector
<32>(&this->data_
, 0);
345 insert_into_vector
<8>(&this->data_
, address_size
);
346 write_unsigned_LEB_128(&this->data_
, abbreviation_number
);
347 this->data_
.insert(this->data_
.end(), debug_info
, die_end
);
349 debug_info
= next_compile_unit
;
351 this->set_data_size(data_
.size());
354 void Output_reduced_debug_info_section::do_write(Output_file
* of
)
356 off_t offset
= this->offset();
357 off_t data_size
= this->data_size();
358 unsigned char* view
= of
->get_output_view(offset
, data_size
);
360 memcpy(view
, this->postprocessing_buffer(),
361 this->postprocessing_buffer_size());
363 memcpy(view
, &this->data_
.front(), data_size
);
364 of
->write_output_view(offset
, data_size
, view
);
367 } // End namespace gold.
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