gold/dwarf_reader.h

   1 // dwarf_reader.h -- parse dwarf2/3 debug information for gold  -*- C++ -*-
   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 #ifndef GOLD_DWARF_READER_H
  24 #define GOLD_DWARF_READER_H
  25
  26 #include <vector>
  27 #include <map>
  28
  29 #include "elfcpp.h"
  30 #include "elfcpp_swap.h"
  31 #include "dwarf.h"
  32 #include "reloc.h"
  33
  34 namespace gold
  35 {
  36
  37 template<int size, bool big_endian>
  38 class Track_relocs;
  39 struct LineStateMachine;
  40
  41 // This class is used to read the line information from the debugging
  42 // section of an object file.
  43
  44 template<int size, bool big_endian>
  45 class Dwarf_line_info
  46 {
  47  public:
  48   // Initializes a .debug_line reader for a given object file.
  49   Dwarf_line_info(Object* object);
  50
  51   // Given a section number and an offset, returns the associated
  52   // file and line-number, as a string: "file:lineno".  If unable
  53   // to do the mapping, returns the empty string.  You must call
  54   // read_line_mappings() before calling this function.
  55   std::string
  56   addr2line(unsigned int shndx, off_t offset);
  57
  58  private:
  59   // Start processing line info, and populates the offset_map_.
  60   void
  61   read_line_mappings();
  62
  63   // Reads the relocation section associated with .debug_line and
  64   // stores relocation information in reloc_map_.
  65   void
  66   read_relocs();
  67
  68   // Looks in the symtab to see what section a symbol is in.
  69   unsigned int
  70   symbol_section(unsigned int sym,
  71                  typename elfcpp::Elf_types<size>::Elf_Addr* value);
  72
  73   // Reads the DWARF2/3 header for this line info.  Each takes as input
  74   // a starting buffer position, and returns the ending position.
  75   const unsigned char*
  76   read_header_prolog(const unsigned char* lineptr);
  77
  78   const unsigned char*
  79   read_header_tables(const unsigned char* lineptr);
  80
  81   // Reads the DWARF2/3 line information.
  82   const unsigned char*
  83   read_lines(const unsigned char* lineptr);
  84
  85   // Process a single line info opcode at START using the state
  86   // machine at LSM.  Return true if we should define a line using the
  87   // current state of the line state machine.  Place the length of the
  88   // opcode in LEN.
  89   bool
  90   process_one_opcode(const unsigned char* start,
  91                      struct LineStateMachine* lsm, size_t* len);
  92
  93   // If we saw anything amiss while parsing, we set this to false.
  94   // Then addr2line will always fail (rather than return possibly-
  95   // corrupt data).
  96   bool data_valid_;
  97
  98   // A DWARF2/3 line info header.  This is not the same size as in the
  99   // actual file, as the one in the file may have a 32 bit or 64 bit
 100   // lengths.
 101
 102   struct Dwarf_line_infoHeader
 103   {
 104     off_t total_length;
 105     int version;
 106     off_t prologue_length;
 107     int min_insn_length; // insn stands for instructin
 108     bool default_is_stmt; // stmt stands for statement
 109     signed char line_base;
 110     int line_range;
 111     unsigned char opcode_base;
 112     std::vector<unsigned char> std_opcode_lengths;
 113     int offset_size;
 114   } header_;
 115
 116   // buffer is the buffer for our line info, starting at exactly where
 117   // the line info to read is.
 118   const unsigned char* buffer_;
 119   const unsigned char* buffer_end_;
 120
 121   // This has relocations that point into buffer.
 122   Track_relocs<size, big_endian> track_relocs_;
 123
 124   // This is used to figure out what section to apply a relocation to.
 125   const unsigned char* symtab_buffer_;
 126   const unsigned char* symtab_buffer_end_;
 127
 128   // Holds the directories and files as we see them.
 129   std::vector<std::string> directories_;
 130   // The first part is an index into directories_, the second the filename.
 131   std::vector< std::pair<int, std::string> > files_;
 132
 133   // A map from offset of the relocation target to the shndx and
 134   // addend for the relocation.
 135   typedef std::map<typename elfcpp::Elf_types<size>::Elf_Addr,
 136                    std::pair<unsigned int,
 137                              typename elfcpp::Elf_types<size>::Elf_Swxword> >
 138   Reloc_map;
 139   Reloc_map reloc_map_;
 140
 141   // We can't do better than to keep the offsets in a sorted vector.
 142   // Here, offset is the key, and file_num/line_num is the value.
 143   struct Offset_to_lineno_entry
 144   {
 145     off_t offset;
 146     int file_num;    // a pointer into files_
 147     int line_num;
 148     // Offsets are unique within a section, so that's a sufficient sort key.
 149     bool operator<(const Offset_to_lineno_entry& that) const
 150     { return this->offset < that.offset; }
 151   };
 152   // We have a vector of offset->lineno entries for every input section.
 153   typedef Unordered_map<unsigned int, std::vector<Offset_to_lineno_entry> >
 154   Lineno_map;
 155
 156   Lineno_map line_number_map_;
 157 };
 158
 159 } // End namespace gold.
 160
 161 #endif // !defined(GOLD_DWARF_READER_H)