darkkirb/old-cross-binutils
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity
old-cross-binutils/gold/dwarf_reader.cc

728 lines
21 KiB
C++
Raw Blame History

// dwarf_reader.cc -- parse dwarf2/3 debug information
// Copyright 2007 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
#include "gold.h"
#include "elfcpp_swap.h"
#include "dwarf.h"
#include "object.h"
#include "parameters.h"
#include "reloc.h"
#include "dwarf_reader.h"
namespace {
// Read an unsigned LEB128 number. Each byte contains 7 bits of
// information, plus one bit saying whether the number continues or
// not.
uint64_t
read_unsigned_LEB_128(const unsigned char* buffer, size_t* len)
{
uint64_t result = 0;
size_t num_read = 0;
unsigned int shift = 0;
unsigned char byte;
do
{
byte = *buffer++;
num_read++;
result |= (static_cast<uint64_t>(byte & 0x7f)) << shift;
shift += 7;
}
while (byte & 0x80);
*len = num_read;
return result;
}
// Read a signed LEB128 number. These are like regular LEB128
// numbers, except the last byte may have a sign bit set.
int64_t
read_signed_LEB_128(const unsigned char* buffer, size_t* len)
{
int64_t result = 0;
int shift = 0;
size_t num_read = 0;
unsigned char byte;
do
{
byte = *buffer++;
num_read++;
result |= (static_cast<uint64_t>(byte & 0x7f) << shift);
shift += 7;
}
while (byte & 0x80);
if ((shift < 8 * static_cast<int>(sizeof(result))) && (byte & 0x40))
result |= -((static_cast<int64_t>(1)) << shift);
*len = num_read;
return result;
}
} // End anonymous namespace.
namespace gold {
// This is the format of a DWARF2/3 line state machine that we process
// opcodes using. There is no need for anything outside the lineinfo
// processor to know how this works.
struct LineStateMachine
{
int file_num;
uint64_t address;
int line_num;
int column_num;
unsigned int shndx; // the section address refers to
bool is_stmt; // stmt means statement.
bool basic_block;
bool end_sequence;
};
static void
ResetLineStateMachine(struct LineStateMachine* lsm, bool default_is_stmt)
{
lsm->file_num = 1;
lsm->address = 0;
lsm->line_num = 1;
lsm->column_num = 0;
lsm->shndx = -1U;
lsm->is_stmt = default_is_stmt;
lsm->basic_block = false;
lsm->end_sequence = false;
}
template<int size, bool big_endian>
Sized_dwarf_line_info<size, big_endian>::Sized_dwarf_line_info(Object* object)
: data_valid_(false), buffer_(NULL), symtab_buffer_(NULL),
directories_(), files_(), current_header_index_(-1)
{
unsigned int debug_shndx;
for (debug_shndx = 0; debug_shndx < object->shnum(); ++debug_shndx)
if (object->section_name(debug_shndx) == ".debug_line")
{
off_t buffer_size;
this->buffer_ = object->section_contents(
debug_shndx, &buffer_size, false);
this->buffer_end_ = this->buffer_ + buffer_size;
break;
}
if (this->buffer_ == NULL)
return;
// Find the relocation section for ".debug_line".
// We expect these for relobjs (.o's) but not dynobjs (.so's).
bool got_relocs = false;
for (unsigned int reloc_shndx = 0;
reloc_shndx < object->shnum();
++reloc_shndx)
{
unsigned int reloc_sh_type = object->section_type(reloc_shndx);
if ((reloc_sh_type == elfcpp::SHT_REL
|| reloc_sh_type == elfcpp::SHT_RELA)
&& object->section_info(reloc_shndx) == debug_shndx)
{
got_relocs = this->track_relocs_.initialize(object, reloc_shndx,
reloc_sh_type);
break;
}
}
// Finally, we need the symtab section to interpret the relocs.
if (got_relocs)
{
unsigned int symtab_shndx;
for (symtab_shndx = 0; symtab_shndx < object->shnum(); ++symtab_shndx)
if (object->section_type(symtab_shndx) == elfcpp::SHT_SYMTAB)
{
this->symtab_buffer_ = object->section_contents(
symtab_shndx, &this->symtab_buffer_size_, false);
break;
}
if (this->symtab_buffer_ == NULL)
return;
}
// Now that we have successfully read all the data, parse the debug
// info.
this->data_valid_ = true;
this->read_line_mappings();
}
// Read the DWARF header.
template<int size, bool big_endian>
const unsigned char*
Sized_dwarf_line_info<size, big_endian>::read_header_prolog(
const unsigned char* lineptr)
{
uint32_t initial_length = elfcpp::Swap<32, big_endian>::readval(lineptr);
lineptr += 4;
// In DWARF2/3, if the initial length is all 1 bits, then the offset
// size is 8 and we need to read the next 8 bytes for the real length.
if (initial_length == 0xffffffff)
{
header_.offset_size = 8;
initial_length = elfcpp::Swap<64, big_endian>::readval(lineptr);
lineptr += 8;
}
else
header_.offset_size = 4;
header_.total_length = initial_length;
gold_assert(lineptr + header_.total_length <= buffer_end_);
header_.version = elfcpp::Swap<16, big_endian>::readval(lineptr);
lineptr += 2;
if (header_.offset_size == 4)
header_.prologue_length = elfcpp::Swap<32, big_endian>::readval(lineptr);
else
header_.prologue_length = elfcpp::Swap<64, big_endian>::readval(lineptr);
lineptr += header_.offset_size;
header_.min_insn_length = *lineptr;
lineptr += 1;
header_.default_is_stmt = *lineptr;
lineptr += 1;
header_.line_base = *reinterpret_cast<const signed char*>(lineptr);
lineptr += 1;
header_.line_range = *lineptr;
lineptr += 1;
header_.opcode_base = *lineptr;
lineptr += 1;
header_.std_opcode_lengths.reserve(header_.opcode_base + 1);
header_.std_opcode_lengths[0] = 0;
for (int i = 1; i < header_.opcode_base; i++)
{
header_.std_opcode_lengths[i] = *lineptr;
lineptr += 1;
}
return lineptr;
}
// The header for a debug_line section is mildly complicated, because
// the line info is very tightly encoded.
template<int size, bool big_endian>
const unsigned char*
Sized_dwarf_line_info<size, big_endian>::read_header_tables(
const unsigned char* lineptr)
{
++this->current_header_index_;
// Create a new directories_ entry and a new files_ entry for our new
// header. We initialize each with a single empty element, because
// dwarf indexes directory and filenames starting at 1.
gold_assert(static_cast<int>(this->directories_.size())
== this->current_header_index_);
gold_assert(static_cast<int>(this->files_.size())
== this->current_header_index_);
this->directories_.push_back(std::vector<std::string>(1));
this->files_.push_back(std::vector<std::pair<int, std::string> >(1));
// It is legal for the directory entry table to be empty.
if (*lineptr)
{
int dirindex = 1;
while (*lineptr)
{
const char* dirname = reinterpret_cast<const char*>(lineptr);
gold_assert(dirindex
== static_cast<int>(this->directories_.back().size()));
this->directories_.back().push_back(dirname);
lineptr += this->directories_.back().back().size() + 1;
dirindex++;
}
}
lineptr++;
// It is also legal for the file entry table to be empty.
if (*lineptr)
{
int fileindex = 1;
size_t len;
while (*lineptr)
{
const char* filename = reinterpret_cast<const char*>(lineptr);
lineptr += strlen(filename) + 1;
uint64_t dirindex = read_unsigned_LEB_128(lineptr, &len);
lineptr += len;
if (dirindex >= this->directories_.back().size())
dirindex = 0;
int dirindexi = static_cast<int>(dirindex);
read_unsigned_LEB_128(lineptr, &len); // mod_time
lineptr += len;
read_unsigned_LEB_128(lineptr, &len); // filelength
lineptr += len;
gold_assert(fileindex
== static_cast<int>(this->files_.back().size()));
this->files_.back().push_back(std::make_pair(dirindexi, filename));
fileindex++;
}
}
lineptr++;
return lineptr;
}
// Process a single opcode in the .debug.line structure.
// Templating on size and big_endian would yield more efficient (and
// simpler) code, but would bloat the binary. Speed isn't important
// here.
template<int size, bool big_endian>
bool
Sized_dwarf_line_info<size, big_endian>::process_one_opcode(
const unsigned char* start, struct LineStateMachine* lsm, size_t* len)
{
size_t oplen = 0;
size_t templen;
unsigned char opcode = *start;
oplen++;
start++;
// If the opcode is great than the opcode_base, it is a special
// opcode. Most line programs consist mainly of special opcodes.
if (opcode >= header_.opcode_base)
{
opcode -= header_.opcode_base;
const int advance_address = ((opcode / header_.line_range)
* header_.min_insn_length);
lsm->address += advance_address;
const int advance_line = ((opcode % header_.line_range)
+ header_.line_base);
lsm->line_num += advance_line;
lsm->basic_block = true;
*len = oplen;
return true;
}
// Otherwise, we have the regular opcodes
switch (opcode)
{
case elfcpp::DW_LNS_copy:
lsm->basic_block = false;
*len = oplen;
return true;
case elfcpp::DW_LNS_advance_pc:
{
const uint64_t advance_address
= read_unsigned_LEB_128(start, &templen);
oplen += templen;
lsm->address += header_.min_insn_length * advance_address;
}
break;
case elfcpp::DW_LNS_advance_line:
{
const uint64_t advance_line = read_signed_LEB_128(start, &templen);
oplen += templen;
lsm->line_num += advance_line;
}
break;
case elfcpp::DW_LNS_set_file:
{
const uint64_t fileno = read_unsigned_LEB_128(start, &templen);
oplen += templen;
lsm->file_num = fileno;
}
break;
case elfcpp::DW_LNS_set_column:
{
const uint64_t colno = read_unsigned_LEB_128(start, &templen);
oplen += templen;
lsm->column_num = colno;
}
break;
case elfcpp::DW_LNS_negate_stmt:
lsm->is_stmt = !lsm->is_stmt;
break;
case elfcpp::DW_LNS_set_basic_block:
lsm->basic_block = true;
break;
case elfcpp::DW_LNS_fixed_advance_pc:
{
int advance_address;
advance_address = elfcpp::Swap<16, big_endian>::readval(start);
oplen += 2;
lsm->address += advance_address;
}
break;
case elfcpp::DW_LNS_const_add_pc:
{
const int advance_address = (header_.min_insn_length
* ((255 - header_.opcode_base)
/ header_.line_range));
lsm->address += advance_address;
}
break;
case elfcpp::DW_LNS_extended_op:
{
const uint64_t extended_op_len
= read_unsigned_LEB_128(start, &templen);
start += templen;
oplen += templen + extended_op_len;
const unsigned char extended_op = *start;
start++;
switch (extended_op)
{
case elfcpp::DW_LNE_end_sequence:
lsm->end_sequence = true;
*len = oplen;
return true;
case elfcpp::DW_LNE_set_address:
{
lsm->address = elfcpp::Swap<size, big_endian>::readval(start);
typename Reloc_map::const_iterator it
= reloc_map_.find(start - this->buffer_);
if (it != reloc_map_.end())
{
// value + addend.
lsm->address += it->second.second;
lsm->shndx = it->second.first;
}
else
{
// If we're a normal .o file, with relocs, every
// set_address should have an associated relocation.
if (this->input_is_relobj())
this->data_valid_ = false;
}
break;
}
case elfcpp::DW_LNE_define_file:
{
const char* filename = reinterpret_cast<const char*>(start);
templen = strlen(filename) + 1;
start += templen;
uint64_t dirindex = read_unsigned_LEB_128(start, &templen);
oplen += templen;
if (dirindex >= this->directories_.back().size())
dirindex = 0;
int dirindexi = static_cast<int>(dirindex);
read_unsigned_LEB_128(start, &templen); // mod_time
oplen += templen;
read_unsigned_LEB_128(start, &templen); // filelength
oplen += templen;
this->files_.back().push_back(std::make_pair(dirindexi,
filename));
}
break;
}
}
break;
default:
{
// Ignore unknown opcode silently
for (int i = 0; i < header_.std_opcode_lengths[opcode]; i++)
{
size_t templen;
read_unsigned_LEB_128(start, &templen);
start += templen;
oplen += templen;
}
}
break;
}
*len = oplen;
return false;
}
// Read the debug information at LINEPTR and store it in the line
// number map.
template<int size, bool big_endian>
unsigned const char*
Sized_dwarf_line_info<size, big_endian>::read_lines(unsigned const char* lineptr)
{
struct LineStateMachine lsm;
// LENGTHSTART is the place the length field is based on. It is the
// point in the header after the initial length field.
const unsigned char* lengthstart = buffer_;
// In 64 bit dwarf, the initial length is 12 bytes, because of the
// 0xffffffff at the start.
if (header_.offset_size == 8)
lengthstart += 12;
else
lengthstart += 4;
while (lineptr < lengthstart + header_.total_length)
{
ResetLineStateMachine(&lsm, header_.default_is_stmt);
while (!lsm.end_sequence)
{
size_t oplength;
bool add_line = this->process_one_opcode(lineptr, &lsm, &oplength);
if (add_line)
{
Offset_to_lineno_entry entry
= { lsm.address, this->current_header_index_,
lsm.file_num, lsm.line_num };
line_number_map_[lsm.shndx].push_back(entry);
}
lineptr += oplength;
}
}
return lengthstart + header_.total_length;
}
// Looks in the symtab to see what section a symbol is in.
template<int size, bool big_endian>
unsigned int
Sized_dwarf_line_info<size, big_endian>::symbol_section(
unsigned int sym,
typename elfcpp::Elf_types<size>::Elf_Addr* value)
{
const int symsize = elfcpp::Elf_sizes<size>::sym_size;
gold_assert(sym * symsize < this->symtab_buffer_size_);
elfcpp::Sym<size, big_endian> elfsym(this->symtab_buffer_ + sym * symsize);
*value = elfsym.get_st_value();
return elfsym.get_st_shndx();
}
// Read the relocations into a Reloc_map.
template<int size, bool big_endian>
void
Sized_dwarf_line_info<size, big_endian>::read_relocs()
{
if (this->symtab_buffer_ == NULL)
return;
typename elfcpp::Elf_types<size>::Elf_Addr value;
off_t reloc_offset;
while ((reloc_offset = this->track_relocs_.next_offset()) != -1)
{
const unsigned int sym = this->track_relocs_.next_symndx();
const unsigned int shndx = this->symbol_section(sym, &value);
this->reloc_map_[reloc_offset] = std::make_pair(shndx, value);
this->track_relocs_.advance(reloc_offset + 1);
}
}
// Read the line number info.
template<int size, bool big_endian>
void
Sized_dwarf_line_info<size, big_endian>::read_line_mappings()
{
gold_assert(this->data_valid_ == true);
read_relocs();
while (this->buffer_ < this->buffer_end_)
{
const unsigned char* lineptr = this->buffer_;
lineptr = this->read_header_prolog(lineptr);
lineptr = this->read_header_tables(lineptr);
lineptr = this->read_lines(lineptr);
this->buffer_ = lineptr;
}
// Sort the lines numbers, so addr2line can use binary search.
for (typename Lineno_map::iterator it = line_number_map_.begin();
it != line_number_map_.end();
++it)
// Each vector needs to be sorted by offset.
std::sort(it->second.begin(), it->second.end());
}
// Some processing depends on whether the input is a .o file or not.
// For instance, .o files have relocs, and have .debug_lines
// information on a per section basis. .so files, on the other hand,
// lack relocs, and offsets are unique, so we can ignore the section
// information.
template<int size, bool big_endian>
bool
Sized_dwarf_line_info<size, big_endian>::input_is_relobj()
{
// Only .o files have relocs and the symtab buffer that goes with them.
return this->symtab_buffer_ != NULL;
}
// Return a string for a file name and line number.
template<int size, bool big_endian>
std::string
Sized_dwarf_line_info<size, big_endian>::do_addr2line(unsigned int shndx,
off_t offset)
{
if (this->data_valid_ == false)
return "";
const Offset_to_lineno_entry lookup_key = { offset, 0, 0, 0 };
const std::vector<Offset_to_lineno_entry>* offsets;
// If we do not have reloc information, then our input is a .so or
// some similar data structure where all the information is held in
// the offset. In that case, we ignore the input shndx.
if (this->input_is_relobj())
offsets = &this->line_number_map_[shndx];
else
offsets = &this->line_number_map_[-1U];
if (offsets->empty())
return "";
typename std::vector<Offset_to_lineno_entry>::const_iterator it
= std::lower_bound(offsets->begin(), offsets->end(), lookup_key);
// If we found an exact match, great, otherwise find the last entry
// before the passed-in offset.
if (it == offsets->end() || it->offset > offset)
{
if (it == offsets->begin())
return "";
--it;
gold_assert(it->offset < offset);
}
// Convert the file_num + line_num into a string.
std::string ret;
gold_assert(it->header_num < static_cast<int>(this->files_.size()));
gold_assert(it->file_num
< static_cast<int>(this->files_[it->header_num].size()));
const std::pair<int, std::string>& filename_pair
= this->files_[it->header_num][it->file_num];
const std::string& filename = filename_pair.second;
gold_assert(it->header_num < static_cast<int>(this->directories_.size()));
gold_assert(filename_pair.first
< static_cast<int>(this->directories_[it->header_num].size()));
const std::string& dirname
= this->directories_[it->header_num][filename_pair.first];
if (!dirname.empty())
{
ret += dirname;
ret += "/";
}
ret += filename;
if (ret.empty())
ret = "(unknown)";
char buffer[64]; // enough to hold a line number
snprintf(buffer, sizeof(buffer), "%d", it->line_num);
ret += ":";
ret += buffer;
return ret;
}
// Dwarf_line_info routines.
std::string
Dwarf_line_info::one_addr2line(Object* object,
unsigned int shndx, off_t offset)
{
if (parameters->get_size() == 32 && !parameters->is_big_endian())
#ifdef HAVE_TARGET_32_LITTLE
return Sized_dwarf_line_info<32, false>(object).addr2line(shndx, offset);
#else
gold_unreachable();
#endif
else if (parameters->get_size() == 32 && parameters->is_big_endian())
#ifdef HAVE_TARGET_32_BIG
return Sized_dwarf_line_info<32, true>(object).addr2line(shndx, offset);
#else
gold_unreachable();
#endif
else if (parameters->get_size() == 64 && !parameters->is_big_endian())
#ifdef HAVE_TARGET_64_LITTLE
return Sized_dwarf_line_info<64, false>(object).addr2line(shndx, offset);
#else
gold_unreachable();
#endif
else if (parameters->get_size() == 64 && parameters->is_big_endian())
#ifdef HAVE_TARGET_64_BIT
return Sized_dwarf_line_info<64, true>(object).addr2line(shndx, offset);
#else
gold_unreachable();
#endif
else
gold_unreachable();
}
#ifdef HAVE_TARGET_32_LITTLE
template
class Sized_dwarf_line_info<32, false>;
#endif
#ifdef HAVE_TARGET_32_BIG
template
class Sized_dwarf_line_info<32, true>;
#endif
#ifdef HAVE_TARGET_64_LITTLE
template
class Sized_dwarf_line_info<64, false>;
#endif
#ifdef HAVE_TARGET_64_BIG
template
class Sized_dwarf_line_info<64, true>;
#endif
} // End namespace gold.
Reference in a new issue View git blame Copy permalink