binutils-gdb/gold/dwarf_reader.h

// dwarf_reader.h -- parse dwarf2/3 debug information for gold  -*- C++ -*-

// 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.

#ifndef GOLD_DWARF_READER_H
#define GOLD_DWARF_READER_H

#include <vector>

#include "elfcpp_swap.h"
#include "dwarf.h"

namespace gold
{

struct LineStateMachine;

// This class is used to read the line information from the debugging
// section of an object file.

class Dwarf_line_info
{
 public:
  // Initializes a .debug_line reader. Buffer and buffer length point
  // to the beginning and length of the line information to read.
  // Reader is a ByteReader class that has the endianness set
  // properly.
  Dwarf_line_info(const unsigned char* buffer, off_t buffer_length)
    : buffer_(buffer), buffer_end_(buffer + buffer_length),
      directories_(1), files_(1)
  { }

  // Start processing line info, and populates the offset_map_.
  template<int size, bool big_endian>
  void
  read_line_mappings()
  {
    while (buffer_ < buffer_end_)
      {
        const unsigned char* lineptr = buffer_;
        lineptr = this->read_header_prolog<size, big_endian>(lineptr);
        lineptr = this->read_header_tables(lineptr);
        lineptr = this->read_lines(size, big_endian, lineptr);
        buffer_ = lineptr;
      }
    finalize_line_number_map();
  }

  // Given a section number and an offset, returns the associated
  // file and line-number, as a string: "file:lineno".  If unable
  // to do the mapping, returns the empty string.  You must call
  // read_line_mappings() before calling this function.
  std::string
  addr2line(unsigned int shndx, off_t offset);

 private:
  // Reads the DWARF2/3 header for this line info.  Each takes as input
  // a starting buffer position, and returns the ending position.
  template<int size, bool big_endian>
  const unsigned char*
  read_header_prolog(const unsigned char* lineptr);

  const unsigned char*
  read_header_tables(const unsigned char* lineptr);

  // Reads the DWARF2/3 line information.
  const unsigned char*
  read_lines(int size, bool big_endian, const unsigned char* lineptr);

  // Process a single line info opcode at START using the state
  // machine at LSM.  Return true if we should define a line using the
  // current state of the line state machine.  Place the length of the
  // opcode in LEN.
  bool
  process_one_opcode(int size, bool big_endian,
                     const unsigned char* start,
                     struct LineStateMachine* lsm, size_t* len);

  // Called after all line number have been read, to ready
  // line_number_map_ for calls to addr2line().
  void
  finalize_line_number_map();

  // A DWARF2/3 line info header.  This is not the same size as in the
  // actual file, as the one in the file may have a 32 bit or 64 bit
  // lengths.

  struct Dwarf_line_infoHeader
  {
    off_t total_length;
    int version;
    off_t prologue_length;
    int min_insn_length; // insn stands for instructin
    bool default_is_stmt; // stmt stands for statement
    signed char line_base;
    int line_range;
    unsigned char opcode_base;
    std::vector<unsigned char> std_opcode_lengths;
    int offset_size;
  } header_;

  // buffer is the buffer for our line info, starting at exactly where
  // the line info to read is.
  const unsigned char* buffer_;
  const unsigned char* const buffer_end_;

  // Holds the directories and files as we see them.
  std::vector<std::string> directories_;
  // The first part is an index into directories_, the second the filename.
  std::vector< std::pair<int, std::string> > files_;

  // We can't do better than to keep the offsets in a sorted vector.
  // Here, offset is the key, and file_num/line_num is the value.
  struct Offset_to_lineno_entry
  {
    off_t offset;
    int file_num;    // a pointer into files_
    int line_num;
    // Offsets are unique within a section, so that's a sufficient sort key.
    bool operator<(const Offset_to_lineno_entry& that) const
    { return this->offset < that.offset; }
  };
  // We have a vector of offset->lineno entries for every input section.
  typedef Unordered_map<unsigned int, std::vector<Offset_to_lineno_entry> >
  Lineno_map;

  Lineno_map line_number_map_;
};

} // End namespace gold.

#endif // !defined(GOLD_DWARF_READER_H)