1 // dwarf_reader.cc -- parse dwarf2/3 debug information
3 // Copyright 2007 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@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 "elfcpp_swap.h"
28 #include "parameters.h"
30 #include "dwarf_reader.h"
34 // Read an unsigned LEB128 number. Each byte contains 7 bits of
35 // information, plus one bit saying whether the number continues or
39 read_unsigned_LEB_128(const unsigned char* buffer
, size_t* len
)
43 unsigned int shift
= 0;
50 result
|= (static_cast<uint64_t>(byte
& 0x7f)) << shift
;
60 // Read a signed LEB128 number. These are like regular LEB128
61 // numbers, except the last byte may have a sign bit set.
64 read_signed_LEB_128(const unsigned char* buffer
, size_t* len
)
75 result
|= (static_cast<uint64_t>(byte
& 0x7f) << shift
);
80 if ((shift
< 8 * static_cast<int>(sizeof(result
))) && (byte
& 0x40))
81 result
|= -((static_cast<int64_t>(1)) << shift
);
86 } // End anonymous namespace.
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.
95 struct LineStateMachine
101 unsigned int shndx
; // the section address refers to
102 bool is_stmt
; // stmt means statement.
108 ResetLineStateMachine(struct LineStateMachine
* lsm
, bool default_is_stmt
)
115 lsm
->is_stmt
= default_is_stmt
;
116 lsm
->basic_block
= false;
117 lsm
->end_sequence
= false;
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)
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")
130 this->buffer_
= object
->section_contents(
131 debug_shndx
, &buffer_size
, false);
132 this->buffer_end_
= this->buffer_
+ buffer_size
;
135 if (this->buffer_
== NULL
)
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();
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
)
150 got_relocs
= this->track_relocs_
.initialize(object
, reloc_shndx
,
156 // Finally, we need the symtab section to interpret the relocs.
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
)
163 this->symtab_buffer_
= object
->section_contents(
164 symtab_shndx
, &this->symtab_buffer_size_
, false);
167 if (this->symtab_buffer_
== NULL
)
171 // Now that we have successfully read all the data, parse the debug
173 this->data_valid_
= true;
174 this->read_line_mappings();
177 // Read the DWARF header.
179 template<int size
, bool big_endian
>
181 Sized_dwarf_line_info
<size
, big_endian
>::read_header_prolog(
182 const unsigned char* lineptr
)
184 uint32_t initial_length
= elfcpp::Swap
<32, big_endian
>::readval(lineptr
);
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)
191 header_
.offset_size
= 8;
192 initial_length
= elfcpp::Swap
<64, big_endian
>::readval(lineptr
);
196 header_
.offset_size
= 4;
198 header_
.total_length
= initial_length
;
200 gold_assert(lineptr
+ header_
.total_length
<= buffer_end_
);
202 header_
.version
= elfcpp::Swap
<16, big_endian
>::readval(lineptr
);
205 if (header_
.offset_size
== 4)
206 header_
.prologue_length
= elfcpp::Swap
<32, big_endian
>::readval(lineptr
);
208 header_
.prologue_length
= elfcpp::Swap
<64, big_endian
>::readval(lineptr
);
209 lineptr
+= header_
.offset_size
;
211 header_
.min_insn_length
= *lineptr
;
214 header_
.default_is_stmt
= *lineptr
;
217 header_
.line_base
= *reinterpret_cast<const signed char*>(lineptr
);
220 header_
.line_range
= *lineptr
;
223 header_
.opcode_base
= *lineptr
;
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
++)
230 header_
.std_opcode_lengths
[i
] = *lineptr
;
237 // The header for a debug_line section is mildly complicated, because
238 // the line info is very tightly encoded.
240 template<int size
, bool big_endian
>
242 Sized_dwarf_line_info
<size
, big_endian
>::read_header_tables(
243 const unsigned char* lineptr
)
245 ++this->current_header_index_
;
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));
257 // It is legal for the directory entry table to be empty.
263 const char* dirname
= reinterpret_cast<const char*>(lineptr
);
265 == static_cast<int>(this->directories_
.back().size()));
266 this->directories_
.back().push_back(dirname
);
267 lineptr
+= this->directories_
.back().back().size() + 1;
273 // It is also legal for the file entry table to be empty.
280 const char* filename
= reinterpret_cast<const char*>(lineptr
);
281 lineptr
+= strlen(filename
) + 1;
283 uint64_t dirindex
= read_unsigned_LEB_128(lineptr
, &len
);
286 if (dirindex
>= this->directories_
.back().size())
288 int dirindexi
= static_cast<int>(dirindex
);
290 read_unsigned_LEB_128(lineptr
, &len
); // mod_time
293 read_unsigned_LEB_128(lineptr
, &len
); // filelength
296 gold_assert(fileindex
297 == static_cast<int>(this->files_
.back().size()));
298 this->files_
.back().push_back(std::make_pair(dirindexi
, filename
));
307 // Process a single opcode in the .debug.line structure.
309 // Templating on size and big_endian would yield more efficient (and
310 // simpler) code, but would bloat the binary. Speed isn't important
313 template<int size
, bool big_endian
>
315 Sized_dwarf_line_info
<size
, big_endian
>::process_one_opcode(
316 const unsigned char* start
, struct LineStateMachine
* lsm
, size_t* len
)
320 unsigned char opcode
= *start
;
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
)
328 opcode
-= header_
.opcode_base
;
329 const int advance_address
= ((opcode
/ header_
.line_range
)
330 * header_
.min_insn_length
);
331 lsm
->address
+= advance_address
;
333 const int advance_line
= ((opcode
% header_
.line_range
)
334 + header_
.line_base
);
335 lsm
->line_num
+= advance_line
;
336 lsm
->basic_block
= true;
341 // Otherwise, we have the regular opcodes
344 case elfcpp::DW_LNS_copy
:
345 lsm
->basic_block
= false;
349 case elfcpp::DW_LNS_advance_pc
:
351 const uint64_t advance_address
352 = read_unsigned_LEB_128(start
, &templen
);
354 lsm
->address
+= header_
.min_insn_length
* advance_address
;
358 case elfcpp::DW_LNS_advance_line
:
360 const uint64_t advance_line
= read_signed_LEB_128(start
, &templen
);
362 lsm
->line_num
+= advance_line
;
366 case elfcpp::DW_LNS_set_file
:
368 const uint64_t fileno
= read_unsigned_LEB_128(start
, &templen
);
370 lsm
->file_num
= fileno
;
374 case elfcpp::DW_LNS_set_column
:
376 const uint64_t colno
= read_unsigned_LEB_128(start
, &templen
);
378 lsm
->column_num
= colno
;
382 case elfcpp::DW_LNS_negate_stmt
:
383 lsm
->is_stmt
= !lsm
->is_stmt
;
386 case elfcpp::DW_LNS_set_basic_block
:
387 lsm
->basic_block
= true;
390 case elfcpp::DW_LNS_fixed_advance_pc
:
393 advance_address
= elfcpp::Swap
<16, big_endian
>::readval(start
);
395 lsm
->address
+= advance_address
;
399 case elfcpp::DW_LNS_const_add_pc
:
401 const int advance_address
= (header_
.min_insn_length
402 * ((255 - header_
.opcode_base
)
403 / header_
.line_range
));
404 lsm
->address
+= advance_address
;
408 case elfcpp::DW_LNS_extended_op
:
410 const uint64_t extended_op_len
411 = read_unsigned_LEB_128(start
, &templen
);
413 oplen
+= templen
+ extended_op_len
;
415 const unsigned char extended_op
= *start
;
420 case elfcpp::DW_LNE_end_sequence
:
421 lsm
->end_sequence
= true;
425 case elfcpp::DW_LNE_set_address
:
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())
433 lsm
->address
+= it
->second
.second
;
434 lsm
->shndx
= it
->second
.first
;
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;
445 case elfcpp::DW_LNE_define_file
:
447 const char* filename
= reinterpret_cast<const char*>(start
);
448 templen
= strlen(filename
) + 1;
451 uint64_t dirindex
= read_unsigned_LEB_128(start
, &templen
);
454 if (dirindex
>= this->directories_
.back().size())
456 int dirindexi
= static_cast<int>(dirindex
);
458 read_unsigned_LEB_128(start
, &templen
); // mod_time
461 read_unsigned_LEB_128(start
, &templen
); // filelength
464 this->files_
.back().push_back(std::make_pair(dirindexi
,
474 // Ignore unknown opcode silently
475 for (int i
= 0; i
< header_
.std_opcode_lengths
[opcode
]; i
++)
478 read_unsigned_LEB_128(start
, &templen
);
489 // Read the debug information at LINEPTR and store it in the line
492 template<int size
, bool big_endian
>
494 Sized_dwarf_line_info
<size
, big_endian
>::read_lines(unsigned const char* lineptr
)
496 struct LineStateMachine lsm
;
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_
;
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)
509 while (lineptr
< lengthstart
+ header_
.total_length
)
511 ResetLineStateMachine(&lsm
, header_
.default_is_stmt
);
512 while (!lsm
.end_sequence
)
515 bool add_line
= this->process_one_opcode(lineptr
, &lsm
, &oplength
);
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
);
527 return lengthstart
+ header_
.total_length
;
530 // Looks in the symtab to see what section a symbol is in.
532 template<int size
, bool big_endian
>
534 Sized_dwarf_line_info
<size
, big_endian
>::symbol_section(
536 typename
elfcpp::Elf_types
<size
>::Elf_Addr
* value
)
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();
545 // Read the relocations into a Reloc_map.
547 template<int size
, bool big_endian
>
549 Sized_dwarf_line_info
<size
, big_endian
>::read_relocs()
551 if (this->symtab_buffer_
== NULL
)
554 typename
elfcpp::Elf_types
<size
>::Elf_Addr value
;
556 while ((reloc_offset
= this->track_relocs_
.next_offset()) != -1)
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);
565 // Read the line number info.
567 template<int size
, bool big_endian
>
569 Sized_dwarf_line_info
<size
, big_endian
>::read_line_mappings()
571 gold_assert(this->data_valid_
== true);
574 while (this->buffer_
< this->buffer_end_
)
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
;
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();
587 // Each vector needs to be sorted by offset.
588 std::sort(it
->second
.begin(), it
->second
.end());
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
597 template<int size
, bool big_endian
>
599 Sized_dwarf_line_info
<size
, big_endian
>::input_is_relobj()
601 // Only .o files have relocs and the symtab buffer that goes with them.
602 return this->symtab_buffer_
!= NULL
;
606 // Return a string for a file name and line number.
608 template<int size
, bool big_endian
>
610 Sized_dwarf_line_info
<size
, big_endian
>::do_addr2line(unsigned int shndx
,
613 if (this->data_valid_
== false)
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
];
624 offsets
= &this->line_number_map_
[-1U];
625 if (offsets
->empty())
628 typename
std::vector
<Offset_to_lineno_entry
>::const_iterator it
629 = std::lower_bound(offsets
->begin(), offsets
->end(), lookup_key
);
631 // If we found an exact match, great, otherwise find the last entry
632 // before the passed-in offset.
633 if (it
->offset
> offset
)
635 if (it
== offsets
->begin())
638 gold_assert(it
->offset
< offset
);
641 // Convert the file_num + line_num into a string.
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
;
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
];
657 if (!dirname
.empty())
666 char buffer
[64]; // enough to hold a line number
667 snprintf(buffer
, sizeof(buffer
), "%d", it
->line_num
);
674 // Dwarf_line_info routines.
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.
681 Dwarf_line_info::one_addr2line(Object
* object
,
682 unsigned int shndx
, off_t offset
)
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
);
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
);
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
);
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
);
712 #ifdef HAVE_TARGET_32_LITTLE
714 class Sized_dwarf_line_info
<32, false>;
717 #ifdef HAVE_TARGET_32_BIG
719 class Sized_dwarf_line_info
<32, true>;
722 #ifdef HAVE_TARGET_64_LITTLE
724 class Sized_dwarf_line_info
<64, false>;
727 #ifdef HAVE_TARGET_64_BIG
729 class Sized_dwarf_line_info
<64, true>;
732 } // End namespace gold.