From Craig Silverstein: Rework debug info code a bit, add option for
[external/binutils.git] / gold / dwarf_reader.cc
1 // dwarf_reader.cc -- parse dwarf2/3 debug information
2
3 // Copyright 2007 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
25 #include "elfcpp_swap.h"
26 #include "dwarf.h"
27 #include "object.h"
28 #include "parameters.h"
29 #include "reloc.h"
30 #include "dwarf_reader.h"
31
32 namespace {
33
34 // Read an unsigned LEB128 number.  Each byte contains 7 bits of
35 // information, plus one bit saying whether the number continues or
36 // not.
37
38 uint64_t
39 read_unsigned_LEB_128(const unsigned char* buffer, size_t* len)
40 {
41   uint64_t result = 0;
42   size_t num_read = 0;
43   unsigned int shift = 0;
44   unsigned char byte;
45
46   do
47     {
48       byte = *buffer++;
49       num_read++;
50       result |= (static_cast<uint64_t>(byte & 0x7f)) << shift;
51       shift += 7;
52     }
53   while (byte & 0x80);
54
55   *len = num_read;
56
57   return result;
58 }
59
60 // Read a signed LEB128 number.  These are like regular LEB128
61 // numbers, except the last byte may have a sign bit set.
62
63 int64_t
64 read_signed_LEB_128(const unsigned char* buffer, size_t* len)
65 {
66   int64_t result = 0;
67   int shift = 0;
68   size_t num_read = 0;
69   unsigned char byte;
70
71   do
72     {
73       byte = *buffer++;
74       num_read++;
75       result |= (static_cast<uint64_t>(byte & 0x7f) << shift);
76       shift += 7;
77     }
78   while (byte & 0x80);
79
80   if ((shift < 8 * static_cast<int>(sizeof(result))) && (byte & 0x40))
81     result |= -((static_cast<int64_t>(1)) << shift);
82   *len = num_read;
83   return result;
84 }
85
86 } // End anonymous namespace.
87
88
89 namespace gold {
90
91 // This is the format of a DWARF2/3 line state machine that we process
92 // opcodes using.  There is no need for anything outside the lineinfo
93 // processor to know how this works.
94
95 struct LineStateMachine
96 {
97   int file_num;
98   uint64_t address;
99   int line_num;
100   int column_num;
101   unsigned int shndx;    // the section address refers to
102   bool is_stmt;          // stmt means statement.
103   bool basic_block;
104   bool end_sequence;
105 };
106
107 static void
108 ResetLineStateMachine(struct LineStateMachine* lsm, bool default_is_stmt)
109 {
110   lsm->file_num = 1;
111   lsm->address = 0;
112   lsm->line_num = 1;
113   lsm->column_num = 0;
114   lsm->shndx = -1U;
115   lsm->is_stmt = default_is_stmt;
116   lsm->basic_block = false;
117   lsm->end_sequence = false;
118 }
119
120 template<int size, bool big_endian>
121 Sized_dwarf_line_info<size, big_endian>::Sized_dwarf_line_info(Object* object)
122   : data_valid_(false), buffer_(NULL), symtab_buffer_(NULL),
123     directories_(), files_(), current_header_index_(-1)
124 {
125   unsigned int debug_shndx;
126   for (debug_shndx = 0; debug_shndx < object->shnum(); ++debug_shndx)
127     if (object->section_name(debug_shndx) == ".debug_line")
128       {
129         off_t buffer_size;
130         this->buffer_ = object->section_contents(
131             debug_shndx, &buffer_size, false);
132         this->buffer_end_ = this->buffer_ + buffer_size;
133         break;
134       }
135   if (this->buffer_ == NULL)
136     return;
137
138   // Find the relocation section for ".debug_line".
139   // We expect these for relobjs (.o's) but not dynobjs (.so's).
140   bool got_relocs = false;
141   for (unsigned int reloc_shndx = 0;
142        reloc_shndx < object->shnum();
143        ++reloc_shndx)
144     {
145       unsigned int reloc_sh_type = object->section_type(reloc_shndx);
146       if ((reloc_sh_type == elfcpp::SHT_REL
147            || reloc_sh_type == elfcpp::SHT_RELA)
148           && object->section_info(reloc_shndx) == debug_shndx)
149         {
150           got_relocs = this->track_relocs_.initialize(object, reloc_shndx,
151                                                       reloc_sh_type);
152           break;
153         }
154     }
155
156   // Finally, we need the symtab section to interpret the relocs.
157   if (got_relocs)
158     {
159       unsigned int symtab_shndx;
160       for (symtab_shndx = 0; symtab_shndx < object->shnum(); ++symtab_shndx)
161         if (object->section_type(symtab_shndx) == elfcpp::SHT_SYMTAB)
162           {
163             this->symtab_buffer_ = object->section_contents(
164                 symtab_shndx, &this->symtab_buffer_size_, false);
165             break;
166           }
167       if (this->symtab_buffer_ == NULL)
168         return;
169     }
170
171   // Now that we have successfully read all the data, parse the debug
172   // info.
173   this->data_valid_ = true;
174   this->read_line_mappings();
175 }
176
177 // Read the DWARF header.
178
179 template<int size, bool big_endian>
180 const unsigned char*
181 Sized_dwarf_line_info<size, big_endian>::read_header_prolog(
182     const unsigned char* lineptr)
183 {
184   uint32_t initial_length = elfcpp::Swap<32, big_endian>::readval(lineptr);
185   lineptr += 4;
186
187   // In DWARF2/3, if the initial length is all 1 bits, then the offset
188   // size is 8 and we need to read the next 8 bytes for the real length.
189   if (initial_length == 0xffffffff)
190     {
191       header_.offset_size = 8;
192       initial_length = elfcpp::Swap<64, big_endian>::readval(lineptr);
193       lineptr += 8;
194     }
195   else
196     header_.offset_size = 4;
197
198   header_.total_length = initial_length;
199
200   gold_assert(lineptr + header_.total_length <= buffer_end_);
201
202   header_.version = elfcpp::Swap<16, big_endian>::readval(lineptr);
203   lineptr += 2;
204
205   if (header_.offset_size == 4)
206     header_.prologue_length = elfcpp::Swap<32, big_endian>::readval(lineptr);
207   else
208     header_.prologue_length = elfcpp::Swap<64, big_endian>::readval(lineptr);
209   lineptr += header_.offset_size;
210
211   header_.min_insn_length = *lineptr;
212   lineptr += 1;
213
214   header_.default_is_stmt = *lineptr;
215   lineptr += 1;
216
217   header_.line_base = *reinterpret_cast<const signed char*>(lineptr);
218   lineptr += 1;
219
220   header_.line_range = *lineptr;
221   lineptr += 1;
222
223   header_.opcode_base = *lineptr;
224   lineptr += 1;
225
226   header_.std_opcode_lengths.reserve(header_.opcode_base + 1);
227   header_.std_opcode_lengths[0] = 0;
228   for (int i = 1; i < header_.opcode_base; i++)
229     {
230       header_.std_opcode_lengths[i] = *lineptr;
231       lineptr += 1;
232     }
233
234   return lineptr;
235 }
236
237 // The header for a debug_line section is mildly complicated, because
238 // the line info is very tightly encoded.
239
240 template<int size, bool big_endian>
241 const unsigned char*
242 Sized_dwarf_line_info<size, big_endian>::read_header_tables(
243     const unsigned char* lineptr)
244 {
245   ++this->current_header_index_;
246
247   // Create a new directories_ entry and a new files_ entry for our new
248   // header.  We initialize each with a single empty element, because
249   // dwarf indexes directory and filenames starting at 1.
250   gold_assert(static_cast<int>(this->directories_.size())
251               == this->current_header_index_);
252   gold_assert(static_cast<int>(this->files_.size())
253               == this->current_header_index_);
254   this->directories_.push_back(std::vector<std::string>(1));
255   this->files_.push_back(std::vector<std::pair<int, std::string> >(1));
256
257   // It is legal for the directory entry table to be empty.
258   if (*lineptr)
259     {
260       int dirindex = 1;
261       while (*lineptr)
262         {
263           const char* dirname = reinterpret_cast<const char*>(lineptr);
264           gold_assert(dirindex
265                       == static_cast<int>(this->directories_.back().size()));
266           this->directories_.back().push_back(dirname);
267           lineptr += this->directories_.back().back().size() + 1;
268           dirindex++;
269         }
270     }
271   lineptr++;
272
273   // It is also legal for the file entry table to be empty.
274   if (*lineptr)
275     {
276       int fileindex = 1;
277       size_t len;
278       while (*lineptr)
279         {
280           const char* filename = reinterpret_cast<const char*>(lineptr);
281           lineptr += strlen(filename) + 1;
282
283           uint64_t dirindex = read_unsigned_LEB_128(lineptr, &len);
284           lineptr += len;
285
286           if (dirindex >= this->directories_.back().size())
287             dirindex = 0;
288           int dirindexi = static_cast<int>(dirindex);
289
290           read_unsigned_LEB_128(lineptr, &len);   // mod_time
291           lineptr += len;
292
293           read_unsigned_LEB_128(lineptr, &len);   // filelength
294           lineptr += len;
295
296           gold_assert(fileindex
297                       == static_cast<int>(this->files_.back().size()));
298           this->files_.back().push_back(std::make_pair(dirindexi, filename));
299           fileindex++;
300         }
301     }
302   lineptr++;
303
304   return lineptr;
305 }
306
307 // Process a single opcode in the .debug.line structure.
308
309 // Templating on size and big_endian would yield more efficient (and
310 // simpler) code, but would bloat the binary.  Speed isn't important
311 // here.
312
313 template<int size, bool big_endian>
314 bool
315 Sized_dwarf_line_info<size, big_endian>::process_one_opcode(
316     const unsigned char* start, struct LineStateMachine* lsm, size_t* len)
317 {
318   size_t oplen = 0;
319   size_t templen;
320   unsigned char opcode = *start;
321   oplen++;
322   start++;
323
324   // If the opcode is great than the opcode_base, it is a special
325   // opcode. Most line programs consist mainly of special opcodes.
326   if (opcode >= header_.opcode_base)
327     {
328       opcode -= header_.opcode_base;
329       const int advance_address = ((opcode / header_.line_range)
330                                    * header_.min_insn_length);
331       lsm->address += advance_address;
332
333       const int advance_line = ((opcode % header_.line_range)
334                                 + header_.line_base);
335       lsm->line_num += advance_line;
336       lsm->basic_block = true;
337       *len = oplen;
338       return true;
339     }
340
341   // Otherwise, we have the regular opcodes
342   switch (opcode)
343     {
344     case elfcpp::DW_LNS_copy:
345       lsm->basic_block = false;
346       *len = oplen;
347       return true;
348
349     case elfcpp::DW_LNS_advance_pc:
350       {
351         const uint64_t advance_address
352             = read_unsigned_LEB_128(start, &templen);
353         oplen += templen;
354         lsm->address += header_.min_insn_length * advance_address;
355       }
356       break;
357
358     case elfcpp::DW_LNS_advance_line:
359       {
360         const uint64_t advance_line = read_signed_LEB_128(start, &templen);
361         oplen += templen;
362         lsm->line_num += advance_line;
363       }
364       break;
365
366     case elfcpp::DW_LNS_set_file:
367       {
368         const uint64_t fileno = read_unsigned_LEB_128(start, &templen);
369         oplen += templen;
370         lsm->file_num = fileno;
371       }
372       break;
373
374     case elfcpp::DW_LNS_set_column:
375       {
376         const uint64_t colno = read_unsigned_LEB_128(start, &templen);
377         oplen += templen;
378         lsm->column_num = colno;
379       }
380       break;
381
382     case elfcpp::DW_LNS_negate_stmt:
383       lsm->is_stmt = !lsm->is_stmt;
384       break;
385
386     case elfcpp::DW_LNS_set_basic_block:
387       lsm->basic_block = true;
388       break;
389
390     case elfcpp::DW_LNS_fixed_advance_pc:
391       {
392         int advance_address;
393         advance_address = elfcpp::Swap<16, big_endian>::readval(start);
394         oplen += 2;
395         lsm->address += advance_address;
396       }
397       break;
398
399     case elfcpp::DW_LNS_const_add_pc:
400       {
401         const int advance_address = (header_.min_insn_length
402                                      * ((255 - header_.opcode_base)
403                                         / header_.line_range));
404         lsm->address += advance_address;
405       }
406       break;
407
408     case elfcpp::DW_LNS_extended_op:
409       {
410         const uint64_t extended_op_len
411             = read_unsigned_LEB_128(start, &templen);
412         start += templen;
413         oplen += templen + extended_op_len;
414
415         const unsigned char extended_op = *start;
416         start++;
417
418         switch (extended_op)
419           {
420           case elfcpp::DW_LNE_end_sequence:
421             lsm->end_sequence = true;
422             *len = oplen;
423             return true;
424
425           case elfcpp::DW_LNE_set_address:
426             {
427               lsm->address = elfcpp::Swap<size, big_endian>::readval(start);
428               typename Reloc_map::const_iterator it
429                   = reloc_map_.find(start - this->buffer_);
430               if (it != reloc_map_.end())
431                 {
432                   // value + addend.
433                   lsm->address += it->second.second;
434                   lsm->shndx = it->second.first;
435                 }
436               else
437                 {
438                   // If we're a normal .o file, with relocs, every
439                   // set_address should have an associated relocation.
440                   if (this->input_is_relobj())
441                     this->data_valid_ = false;
442                 }
443               break;
444             }
445           case elfcpp::DW_LNE_define_file:
446             {
447               const char* filename  = reinterpret_cast<const char*>(start);
448               templen = strlen(filename) + 1;
449               start += templen;
450
451               uint64_t dirindex = read_unsigned_LEB_128(start, &templen);
452               oplen += templen;
453
454               if (dirindex >= this->directories_.back().size())
455                 dirindex = 0;
456               int dirindexi = static_cast<int>(dirindex);
457
458               read_unsigned_LEB_128(start, &templen);   // mod_time
459               oplen += templen;
460
461               read_unsigned_LEB_128(start, &templen);   // filelength
462               oplen += templen;
463
464               this->files_.back().push_back(std::make_pair(dirindexi,
465                                                            filename));
466             }
467             break;
468           }
469       }
470       break;
471
472     default:
473       {
474         // Ignore unknown opcode  silently
475         for (int i = 0; i < header_.std_opcode_lengths[opcode]; i++)
476           {
477             size_t templen;
478             read_unsigned_LEB_128(start, &templen);
479             start += templen;
480             oplen += templen;
481           }
482       }
483       break;
484   }
485   *len = oplen;
486   return false;
487 }
488
489 // Read the debug information at LINEPTR and store it in the line
490 // number map.
491
492 template<int size, bool big_endian>
493 unsigned const char*
494 Sized_dwarf_line_info<size, big_endian>::read_lines(unsigned const char* lineptr)
495 {
496   struct LineStateMachine lsm;
497
498   // LENGTHSTART is the place the length field is based on.  It is the
499   // point in the header after the initial length field.
500   const unsigned char* lengthstart = buffer_;
501
502   // In 64 bit dwarf, the initial length is 12 bytes, because of the
503   // 0xffffffff at the start.
504   if (header_.offset_size == 8)
505     lengthstart += 12;
506   else
507     lengthstart += 4;
508
509   while (lineptr < lengthstart + header_.total_length)
510     {
511       ResetLineStateMachine(&lsm, header_.default_is_stmt);
512       while (!lsm.end_sequence)
513         {
514           size_t oplength;
515           bool add_line = this->process_one_opcode(lineptr, &lsm, &oplength);
516           if (add_line)
517             {
518               Offset_to_lineno_entry entry
519                   = { lsm.address, this->current_header_index_,
520                       lsm.file_num, lsm.line_num };
521               line_number_map_[lsm.shndx].push_back(entry);
522             }
523           lineptr += oplength;
524         }
525     }
526
527   return lengthstart + header_.total_length;
528 }
529
530 // Looks in the symtab to see what section a symbol is in.
531
532 template<int size, bool big_endian>
533 unsigned int
534 Sized_dwarf_line_info<size, big_endian>::symbol_section(
535     unsigned int sym,
536     typename elfcpp::Elf_types<size>::Elf_Addr* value)
537 {
538   const int symsize = elfcpp::Elf_sizes<size>::sym_size;
539   gold_assert(sym * symsize < this->symtab_buffer_size_);
540   elfcpp::Sym<size, big_endian> elfsym(this->symtab_buffer_ + sym * symsize);
541   *value = elfsym.get_st_value();
542   return elfsym.get_st_shndx();
543 }
544
545 // Read the relocations into a Reloc_map.
546
547 template<int size, bool big_endian>
548 void
549 Sized_dwarf_line_info<size, big_endian>::read_relocs()
550 {
551   if (this->symtab_buffer_ == NULL)
552     return;
553
554   typename elfcpp::Elf_types<size>::Elf_Addr value;
555   off_t reloc_offset;
556   while ((reloc_offset = this->track_relocs_.next_offset()) != -1)
557     {
558       const unsigned int sym = this->track_relocs_.next_symndx();
559       const unsigned int shndx = this->symbol_section(sym, &value);
560       this->reloc_map_[reloc_offset] = std::make_pair(shndx, value);
561       this->track_relocs_.advance(reloc_offset + 1);
562     }
563 }
564
565 // Read the line number info.
566
567 template<int size, bool big_endian>
568 void
569 Sized_dwarf_line_info<size, big_endian>::read_line_mappings()
570 {
571   gold_assert(this->data_valid_ == true);
572
573   read_relocs();
574   while (this->buffer_ < this->buffer_end_)
575     {
576       const unsigned char* lineptr = this->buffer_;
577       lineptr = this->read_header_prolog(lineptr);
578       lineptr = this->read_header_tables(lineptr);
579       lineptr = this->read_lines(lineptr);
580       this->buffer_ = lineptr;
581     }
582
583   // Sort the lines numbers, so addr2line can use binary search.
584   for (typename Lineno_map::iterator it = line_number_map_.begin();
585        it != line_number_map_.end();
586        ++it)
587     // Each vector needs to be sorted by offset.
588     std::sort(it->second.begin(), it->second.end());
589 }
590
591 // Some processing depends on whether the input is a .o file or not.
592 // For instance, .o files have relocs, and have .debug_lines
593 // information on a per section basis.  .so files, on the other hand,
594 // lack relocs, and offsets are unique, so we can ignore the section
595 // information.
596
597 template<int size, bool big_endian>
598 bool
599 Sized_dwarf_line_info<size, big_endian>::input_is_relobj()
600 {
601   // Only .o files have relocs and the symtab buffer that goes with them.
602   return this->symtab_buffer_ != NULL;
603 }
604
605
606 // Return a string for a file name and line number.
607
608 template<int size, bool big_endian>
609 std::string
610 Sized_dwarf_line_info<size, big_endian>::do_addr2line(unsigned int shndx,
611                                                       off_t offset)
612 {
613   if (this->data_valid_ == false)
614     return "";
615
616   const Offset_to_lineno_entry lookup_key = { offset, 0, 0, 0 };
617   const std::vector<Offset_to_lineno_entry>* offsets;
618   // If we do not have reloc information, then our input is a .so or
619   // some similar data structure where all the information is held in
620   // the offset.  In that case, we ignore the input shndx.
621   if (this->input_is_relobj())
622     offsets = &this->line_number_map_[shndx];
623   else
624     offsets = &this->line_number_map_[-1U];
625   if (offsets->empty())
626     return "";
627
628   typename std::vector<Offset_to_lineno_entry>::const_iterator it
629       = std::lower_bound(offsets->begin(), offsets->end(), lookup_key);
630
631   // If we found an exact match, great, otherwise find the last entry
632   // before the passed-in offset.
633   if (it->offset > offset)
634     {
635       if (it == offsets->begin())
636         return "";
637       --it;
638       gold_assert(it->offset < offset);
639     }
640
641   // Convert the file_num + line_num into a string.
642   std::string ret;
643
644   gold_assert(it->header_num < static_cast<int>(this->files_.size()));
645   gold_assert(it->file_num
646               < static_cast<int>(this->files_[it->header_num].size()));
647   const std::pair<int, std::string>& filename_pair
648       = this->files_[it->header_num][it->file_num];
649   const std::string& filename = filename_pair.second;
650
651   gold_assert(it->header_num < static_cast<int>(this->directories_.size()));
652   gold_assert(filename_pair.first
653               < static_cast<int>(this->directories_[it->header_num].size()));
654   const std::string& dirname
655       = this->directories_[it->header_num][filename_pair.first];
656
657   if (!dirname.empty())
658     {
659       ret += dirname;
660       ret += "/";
661     }
662   ret += filename;
663   if (ret.empty())
664     ret = "(unknown)";
665
666   char buffer[64];   // enough to hold a line number
667   snprintf(buffer, sizeof(buffer), "%d", it->line_num);
668   ret += ":";
669   ret += buffer;
670
671   return ret;
672 }
673
674 // Dwarf_line_info routines.
675
676 // Note: this routine instantiates the appropriate
677 // Sized_dwarf_line_info templates for this config, so we don't have
678 // to have a separte instantiation section for them.
679
680 std::string
681 Dwarf_line_info::one_addr2line(Object* object,
682                                unsigned int shndx, off_t offset)
683 {
684   if (parameters->get_size() == 32 && !parameters->is_big_endian())
685 #ifdef HAVE_TARGET_32_LITTLE
686     return Sized_dwarf_line_info<32, false>(object).addr2line(shndx, offset);
687 #else
688     gold_unreachable();
689 #endif
690   else if (parameters->get_size() == 32 && parameters->is_big_endian())
691 #ifdef HAVE_TARGET_32_BIG
692     return Sized_dwarf_line_info<32, true>(object).addr2line(shndx, offset);
693 #else
694     gold_unreachable();
695 #endif
696   else if (parameters->get_size() == 64 && !parameters->is_big_endian())
697 #ifdef HAVE_TARGET_64_LITTLE
698     return Sized_dwarf_line_info<64, false>(object).addr2line(shndx, offset);
699 #else
700     gold_unreachable();
701 #endif
702   else if (parameters->get_size() == 64 && parameters->is_big_endian())
703 #ifdef HAVE_TARGET_64_BIT
704     return Sized_dwarf_line_info<64, true>(object).addr2line(shndx, offset);
705 #else
706     gold_unreachable();
707 #endif
708   else
709     gold_unreachable();
710 }
711
712 #ifdef HAVE_TARGET_32_LITTLE
713 template
714 class Sized_dwarf_line_info<32, false>;
715 #endif
716
717 #ifdef HAVE_TARGET_32_BIG
718 template
719 class Sized_dwarf_line_info<32, true>;
720 #endif
721
722 #ifdef HAVE_TARGET_64_LITTLE
723 template
724 class Sized_dwarf_line_info<64, false>;
725 #endif
726
727 #ifdef HAVE_TARGET_64_BIG
728 template
729 class Sized_dwarf_line_info<64, true>;
730 #endif
731
732 } // End namespace gold.