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binutils-gdb/gold/dwarf_reader.cc

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// dwarf_reader.cc -- parse dwarf2/3 debug information
// Copyright 2007, 2008, 2009, 2010, 2011 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 <algorithm>
#include <vector>
#include "elfcpp_swap.h"
#include "dwarf.h"
#include "object.h"
#include "parameters.h"
#include "reloc.h"
#include "dwarf_reader.h"
#include "int_encoding.h"
#include "compressed_output.h"
namespace gold {
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,
unsigned int read_shndx)
: data_valid_(false), buffer_(NULL), buffer_start_(NULL),
symtab_buffer_(NULL), directories_(), files_(), current_header_index_(-1)
{
unsigned int debug_shndx;
for (debug_shndx = 1; debug_shndx < object->shnum(); ++debug_shndx)
{
// FIXME: do this more efficiently: section_name() isn't super-fast
std::string name = object->section_name(debug_shndx);
if (name == ".debug_line" || name == ".zdebug_line")
{
section_size_type buffer_size;
bool is_new = false;
this->buffer_ = object->decompressed_section_contents(debug_shndx,
&buffer_size,
&is_new);
if (is_new)
this->buffer_start_ = this->buffer_;
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);
this->track_relocs_type_ = 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(object, read_shndx);
}
// 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_unaligned<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_unaligned<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_unaligned<16, big_endian>::readval(lineptr);
lineptr += 2;
if (header_.offset_size == 4)
header_.prologue_length = elfcpp::Swap_unaligned<32, big_endian>::readval(lineptr);
else
header_.prologue_length = elfcpp::Swap_unaligned<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.resize(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.
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_unaligned<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:
// This means that the current byte is the one immediately
// after a set of instructions. Record the current line
// for up to one less than the current address.
lsm->line_num = -1;
lsm->end_sequence = true;
*len = oplen;
return true;
case elfcpp::DW_LNE_set_address:
{
lsm->address =
elfcpp::Swap_unaligned<size, big_endian>::readval(start);
typename Reloc_map::const_iterator it
= this->reloc_map_.find(start - this->buffer_);
if (it != reloc_map_.end())
{
// If this is a SHT_RELA section, then ignore the
// section contents. This assumes that this is a
// straight reloc which just uses the reloc addend.
// The reloc addend has already been included in the
// symbol value.
if (this->track_relocs_type_ == elfcpp::SHT_RELA)
lsm->address = 0;
// Add in the symbol value.
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);
if (dirindex >= this->directories_.back().size())
dirindex = 0;
int dirindexi = static_cast<int>(dirindex);
// This opcode takes two additional ULEB128 parameters
// (mod_time and filelength), but we don't use those
// values. Because OPLEN already tells us how far to
// skip to the next opcode, we don't need to read
// them at all.
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,
unsigned int shndx)
{
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
&& (shndx == -1U || lsm.shndx == -1U || shndx == lsm.shndx))
{
Offset_to_lineno_entry entry
= { static_cast<off_t>(lsm.address),
this->current_header_index_,
static_cast<unsigned int>(lsm.file_num),
true, lsm.line_num };
std::vector<Offset_to_lineno_entry>&
map(this->line_number_map_[lsm.shndx]);
// If we see two consecutive entries with the same
// offset and a real line number, then mark the first
// one as non-canonical.
if (!map.empty()
&& (map.back().offset == static_cast<off_t>(lsm.address))
&& lsm.line_num != -1
&& map.back().line_num != -1)
map.back().last_line_for_offset = false;
map.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(
Object* object,
unsigned int sym,
typename elfcpp::Elf_types<size>::Elf_Addr* value,
bool* is_ordinary)
{
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 object->adjust_sym_shndx(sym, elfsym.get_st_shndx(), is_ordinary);
}
// Read the relocations into a Reloc_map.
template<int size, bool big_endian>
void
Sized_dwarf_line_info<size, big_endian>::read_relocs(Object* object)
{
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();
bool is_ordinary;
const unsigned int shndx = this->symbol_section(object, sym, &value,
&is_ordinary);
// There is no reason to record non-ordinary section indexes, or
// SHN_UNDEF, because they will never match the real section.
if (is_ordinary && shndx != elfcpp::SHN_UNDEF)
{
value += this->track_relocs_.next_addend();
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(Object* object,
unsigned int shndx)
{
gold_assert(this->data_valid_ == true);
this->read_relocs(object);
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, shndx);
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;
}
// Given an Offset_to_lineno_entry vector, and an offset, figure out
// if the offset points into a function according to the vector (see
// comments below for the algorithm). If it does, return an iterator
// into the vector that points to the line-number that contains that
// offset. If not, it returns vector::end().
static std::vector<Offset_to_lineno_entry>::const_iterator
offset_to_iterator(const std::vector<Offset_to_lineno_entry>* offsets,
off_t offset)
{
const Offset_to_lineno_entry lookup_key = { offset, 0, 0, true, 0 };
// lower_bound() returns the smallest offset which is >= lookup_key.
// If no offset in offsets is >= lookup_key, returns end().
std::vector<Offset_to_lineno_entry>::const_iterator it
= std::lower_bound(offsets->begin(), offsets->end(), lookup_key);
// This code is easiest to understand with a concrete example.
// Here's a possible offsets array:
// {{offset = 3211, header_num = 0, file_num = 1, last, line_num = 16}, // 0
// {offset = 3224, header_num = 0, file_num = 1, last, line_num = 20}, // 1
// {offset = 3226, header_num = 0, file_num = 1, last, line_num = 22}, // 2
// {offset = 3231, header_num = 0, file_num = 1, last, line_num = 25}, // 3
// {offset = 3232, header_num = 0, file_num = 1, last, line_num = -1}, // 4
// {offset = 3232, header_num = 0, file_num = 1, last, line_num = 65}, // 5
// {offset = 3235, header_num = 0, file_num = 1, last, line_num = 66}, // 6
// {offset = 3236, header_num = 0, file_num = 1, last, line_num = -1}, // 7
// {offset = 5764, header_num = 0, file_num = 1, last, line_num = 48}, // 8
// {offset = 5764, header_num = 0, file_num = 1,!last, line_num = 47}, // 9
// {offset = 5765, header_num = 0, file_num = 1, last, line_num = 49}, // 10
// {offset = 5767, header_num = 0, file_num = 1, last, line_num = 50}, // 11
// {offset = 5768, header_num = 0, file_num = 1, last, line_num = 51}, // 12
// {offset = 5773, header_num = 0, file_num = 1, last, line_num = -1}, // 13
// {offset = 5787, header_num = 1, file_num = 1, last, line_num = 19}, // 14
// {offset = 5790, header_num = 1, file_num = 1, last, line_num = 20}, // 15
// {offset = 5793, header_num = 1, file_num = 1, last, line_num = 67}, // 16
// {offset = 5793, header_num = 1, file_num = 1, last, line_num = -1}, // 17
// {offset = 5793, header_num = 1, file_num = 1,!last, line_num = 66}, // 18
// {offset = 5795, header_num = 1, file_num = 1, last, line_num = 68}, // 19
// {offset = 5798, header_num = 1, file_num = 1, last, line_num = -1}, // 20
// The entries with line_num == -1 mark the end of a function: the
// associated offset is one past the last instruction in the
// function. This can correspond to the beginning of the next
// function (as is true for offset 3232); alternately, there can be
// a gap between the end of one function and the start of the next
// (as is true for some others, most obviously from 3236->5764).
//
// Case 1: lookup_key has offset == 10. lower_bound returns
// offsets[0]. Since it's not an exact match and we're
// at the beginning of offsets, we return end() (invalid).
// Case 2: lookup_key has offset 10000. lower_bound returns
// offset[21] (end()). We return end() (invalid).
// Case 3: lookup_key has offset == 3211. lower_bound matches
// offsets[0] exactly, and that's the entry we return.
// Case 4: lookup_key has offset == 3232. lower_bound returns
// offsets[4]. That's an exact match, but indicates
// end-of-function. We check if offsets[5] is also an
// exact match but not end-of-function. It is, so we
// return offsets[5].
// Case 5: lookup_key has offset == 3214. lower_bound returns
// offsets[1]. Since it's not an exact match, we back
// up to the offset that's < lookup_key, offsets[0].
// We note offsets[0] is a valid entry (not end-of-function),
// so that's the entry we return.
// Case 6: lookup_key has offset == 4000. lower_bound returns
// offsets[8]. Since it's not an exact match, we back
// up to offsets[7]. Since offsets[7] indicates
// end-of-function, we know lookup_key is between
// functions, so we return end() (not a valid offset).
// Case 7: lookup_key has offset == 5794. lower_bound returns
// offsets[19]. Since it's not an exact match, we back
// up to offsets[16]. Note we back up to the *first*
// entry with offset 5793, not just offsets[19-1].
// We note offsets[16] is a valid entry, so we return it.
// If offsets[16] had had line_num == -1, we would have
// checked offsets[17]. The reason for this is that
// 16 and 17 can be in an arbitrary order, since we sort
// only by offset and last_line_for_offset. (Note it
// doesn't help to use line_number as a tertiary sort key,
// since sometimes we want the -1 to be first and sometimes
// we want it to be last.)
// This deals with cases (1) and (2).
if ((it == offsets->begin() && offset < it->offset)
|| it == offsets->end())
return offsets->end();
// This deals with cases (3) and (4).
if (offset == it->offset)
{
while (it != offsets->end()
&& it->offset == offset
&& it->line_num == -1)
++it;
if (it == offsets->end() || it->offset != offset)
return offsets->end();
else
return it;
}
// This handles the first part of case (7) -- we back up to the
// *first* entry that has the offset that's behind us.
gold_assert(it != offsets->begin());
std::vector<Offset_to_lineno_entry>::const_iterator range_end = it;
--it;
const off_t range_value = it->offset;
while (it != offsets->begin() && (it-1)->offset == range_value)
--it;
// This handles cases (5), (6), and (7): if any entry in the
// equal_range [it, range_end) has a line_num != -1, it's a valid
// match. If not, we're not in a function. The line number we saw
// last for an offset will be sorted first, so it'll get returned if
// it's present.
for (; it != range_end; ++it)
if (it->line_num != -1)
return it;
return offsets->end();
}
// Returns the canonical filename:lineno for the address passed in.
// If other_lines is not NULL, appends the non-canonical lines
// assigned to the same address.
template<int size, bool big_endian>
std::string
Sized_dwarf_line_info<size, big_endian>::do_addr2line(
unsigned int shndx,
off_t offset,
std::vector<std::string>* other_lines)
{
if (this->data_valid_ == false)
return "";
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
= offset_to_iterator(offsets, offset);
if (it == offsets->end())
return "";
std::string result = this->format_file_lineno(*it);
if (other_lines != NULL)
for (++it; it != offsets->end() && it->offset == offset; ++it)
{
if (it->line_num == -1)
continue; // The end of a previous function.
other_lines->push_back(this->format_file_lineno(*it));
}
return result;
}
// Convert the file_num + line_num into a string.
template<int size, bool big_endian>
std::string
Sized_dwarf_line_info<size, big_endian>::format_file_lineno(
const Offset_to_lineno_entry& loc) const
{
std::string ret;
gold_assert(loc.header_num < static_cast<int>(this->files_.size()));
gold_assert(loc.file_num
< static_cast<int>(this->files_[loc.header_num].size()));
const std::pair<int, std::string>& filename_pair
= this->files_[loc.header_num][loc.file_num];
const std::string& filename = filename_pair.second;
gold_assert(loc.header_num < static_cast<int>(this->directories_.size()));
gold_assert(filename_pair.first
< static_cast<int>(this->directories_[loc.header_num].size()));
const std::string& dirname
= this->directories_[loc.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", loc.line_num);
ret += ":";
ret += buffer;
return ret;
}
// Dwarf_line_info routines.
static unsigned int next_generation_count = 0;
struct Addr2line_cache_entry
{
Object* object;
unsigned int shndx;
Dwarf_line_info* dwarf_line_info;
unsigned int generation_count;
unsigned int access_count;
Addr2line_cache_entry(Object* o, unsigned int s, Dwarf_line_info* d)
: object(o), shndx(s), dwarf_line_info(d),
generation_count(next_generation_count), access_count(0)
{
if (next_generation_count < (1U << 31))
++next_generation_count;
}
};
// We expect this cache to be small, so don't bother with a hashtable
// or priority queue or anything: just use a simple vector.
static std::vector<Addr2line_cache_entry> addr2line_cache;
std::string
Dwarf_line_info::one_addr2line(Object* object,
unsigned int shndx, off_t offset,
size_t cache_size,
std::vector<std::string>* other_lines)
{
Dwarf_line_info* lineinfo = NULL;
std::vector<Addr2line_cache_entry>::iterator it;
// First, check the cache. If we hit, update the counts.
for (it = addr2line_cache.begin(); it != addr2line_cache.end(); ++it)
{
if (it->object == object && it->shndx == shndx)
{
lineinfo = it->dwarf_line_info;
it->generation_count = next_generation_count;
// We cap generation_count at 2^31 -1 to avoid overflow.
if (next_generation_count < (1U << 31))
++next_generation_count;
// We cap access_count at 31 so 2^access_count doesn't overflow
if (it->access_count < 31)
++it->access_count;
break;
}
}
// If we don't hit the cache, create a new object and insert into the
// cache.
if (lineinfo == NULL)
{
switch (parameters->size_and_endianness())
{
#ifdef HAVE_TARGET_32_LITTLE
case Parameters::TARGET_32_LITTLE:
lineinfo = new Sized_dwarf_line_info<32, false>(object, shndx); break;
#endif
#ifdef HAVE_TARGET_32_BIG
case Parameters::TARGET_32_BIG:
lineinfo = new Sized_dwarf_line_info<32, true>(object, shndx); break;
#endif
#ifdef HAVE_TARGET_64_LITTLE
case Parameters::TARGET_64_LITTLE:
lineinfo = new Sized_dwarf_line_info<64, false>(object, shndx); break;
#endif
#ifdef HAVE_TARGET_64_BIG
case Parameters::TARGET_64_BIG:
lineinfo = new Sized_dwarf_line_info<64, true>(object, shndx); break;
#endif
default:
gold_unreachable();
}
addr2line_cache.push_back(Addr2line_cache_entry(object, shndx, lineinfo));
}
// Now that we have our object, figure out the answer
std::string retval = lineinfo->addr2line(shndx, offset, other_lines);
// Finally, if our cache has grown too big, delete old objects. We
// assume the common (probably only) case is deleting only one object.
// We use a pretty simple scheme to evict: function of LRU and MFU.
while (addr2line_cache.size() > cache_size)
{
unsigned int lowest_score = ~0U;
std::vector<Addr2line_cache_entry>::iterator lowest
= addr2line_cache.end();
for (it = addr2line_cache.begin(); it != addr2line_cache.end(); ++it)
{
const unsigned int score = (it->generation_count
+ (1U << it->access_count));
if (score < lowest_score)
{
lowest_score = score;
lowest = it;
}
}
if (lowest != addr2line_cache.end())
{
delete lowest->dwarf_line_info;
addr2line_cache.erase(lowest);
}
}
return retval;
}
void
Dwarf_line_info::clear_addr2line_cache()
{
for (std::vector<Addr2line_cache_entry>::iterator it = addr2line_cache.begin();
it != addr2line_cache.end();
++it)
delete it->dwarf_line_info;
addr2line_cache.clear();
}
#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.
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