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 // We can't do better than to keep the offsets in a sorted vector.
  42 // Here, offset is the key, and file_num/line_num is the value.
  43 struct Offset_to_lineno_entry
  44 {
  45   off_t offset;
  46   int header_num;  // which file-list to use (i.e. which .o file are we in)
  47   int file_num;    // a pointer into files_
  48   int line_num;    // the line number in the source file
  49   // Offsets are unique within a section, so that's a sufficient sort key.
  50   bool operator<(const Offset_to_lineno_entry& that) const
  51   { return this->offset < that.offset; }
  52 };
  53
  54 // This class is used to read the line information from the debugging
  55 // section of an object file.
  56
  57 class Dwarf_line_info
  58 {
  59  public:
  60   Dwarf_line_info()
  61   { }
  62
  63   virtual
  64   ~Dwarf_line_info()
  65   { }
  66
  67   // Given a section number and an offset, returns the associated
  68   // file and line-number, as a string: "file:lineno".  If unable
  69   // to do the mapping, returns the empty string.  You must call
  70   // read_line_mappings() before calling this function.
  71   std::string
  72   addr2line(unsigned int shndx, off_t offset)
  73   { return do_addr2line(shndx, offset); }
  74
  75   // A helper function for a single addr2line lookup.  It uses
  76   // parameters() to figure out the size and endianness.  This is less
  77   // efficient than using the templatized size and endianness, so only
  78   // call this from an un-templatized context.
  79   static std::string
  80   one_addr2line(Object* object, unsigned int shndx, off_t offset);
  81
  82  private:
  83   virtual std::string
  84   do_addr2line(unsigned int shndx, off_t offset) = 0;
  85 };
  86
  87 template<int size, bool big_endian>
  88 class Sized_dwarf_line_info : public Dwarf_line_info
  89 {
  90  public:
  91   // Initializes a .debug_line reader for a given object file.
  92   // If SHNDX is specified and non-negative, only read the debug
  93   // information that pertains to the specified section.
  94   Sized_dwarf_line_info(Object* object, off_t read_shndx = -1U);
  95
  96  private:
  97   std::string
  98   do_addr2line(unsigned int shndx, off_t offset);
  99
 100   // Start processing line info, and populates the offset_map_.
 101   // If SHNDX is non-negative, only store debug information that
 102   // pertains to the specified section.
 103   void
 104   read_line_mappings(off_t shndx);
 105
 106   // Reads the relocation section associated with .debug_line and
 107   // stores relocation information in reloc_map_.
 108   void
 109   read_relocs();
 110
 111   // Looks in the symtab to see what section a symbol is in.
 112   unsigned int
 113   symbol_section(unsigned int sym,
 114                  typename elfcpp::Elf_types<size>::Elf_Addr* value);
 115
 116   // Reads the DWARF2/3 header for this line info.  Each takes as input
 117   // a starting buffer position, and returns the ending position.
 118   const unsigned char*
 119   read_header_prolog(const unsigned char* lineptr);
 120
 121   const unsigned char*
 122   read_header_tables(const unsigned char* lineptr);
 123
 124   // Reads the DWARF2/3 line information.  If shndx is non-negative,
 125   // discard all line information that doesn't pertain to the given
 126   // section.
 127   const unsigned char*
 128   read_lines(const unsigned char* lineptr, off_t shndx);
 129
 130   // Process a single line info opcode at START using the state
 131   // machine at LSM.  Return true if we should define a line using the
 132   // current state of the line state machine.  Place the length of the
 133   // opcode in LEN.
 134   bool
 135   process_one_opcode(const unsigned char* start,
 136                      struct LineStateMachine* lsm, size_t* len);
 137
 138   // Some parts of processing differ depending on whether the input
 139   // was a .o file or not.
 140   bool input_is_relobj();
 141
 142   // If we saw anything amiss while parsing, we set this to false.
 143   // Then addr2line will always fail (rather than return possibly-
 144   // corrupt data).
 145   bool data_valid_;
 146
 147   // A DWARF2/3 line info header.  This is not the same size as in the
 148   // actual file, as the one in the file may have a 32 bit or 64 bit
 149   // lengths.
 150
 151   struct Dwarf_line_infoHeader
 152   {
 153     off_t total_length;
 154     int version;
 155     off_t prologue_length;
 156     int min_insn_length; // insn stands for instructin
 157     bool default_is_stmt; // stmt stands for statement
 158     signed char line_base;
 159     int line_range;
 160     unsigned char opcode_base;
 161     std::vector<unsigned char> std_opcode_lengths;
 162     int offset_size;
 163   } header_;
 164
 165   // buffer is the buffer for our line info, starting at exactly where
 166   // the line info to read is.
 167   const unsigned char* buffer_;
 168   const unsigned char* buffer_end_;
 169
 170   // This has relocations that point into buffer.
 171   Track_relocs<size, big_endian> track_relocs_;
 172
 173   // This is used to figure out what section to apply a relocation to.
 174   const unsigned char* symtab_buffer_;
 175   section_size_type symtab_buffer_size_;
 176
 177   // Holds the directories and files as we see them.  We have an array
 178   // of directory-lists, one for each .o file we're reading (usually
 179   // there will just be one, but there may be more if input is a .so).
 180   std::vector<std::vector<std::string> > directories_;
 181   // The first part is an index into directories_, the second the filename.
 182   std::vector<std::vector< std::pair<int, std::string> > > files_;
 183
 184   // An index into the current directories_ and files_ vectors.
 185   int current_header_index_;
 186
 187   // A sorted map from offset of the relocation target to the shndx
 188   // and addend for the relocation.
 189   typedef std::map<typename elfcpp::Elf_types<size>::Elf_Addr,
 190                    std::pair<unsigned int,
 191                              typename elfcpp::Elf_types<size>::Elf_Swxword> >
 192   Reloc_map;
 193   Reloc_map reloc_map_;
 194
 195   // We have a vector of offset->lineno entries for every input section.
 196   typedef Unordered_map<unsigned int, std::vector<Offset_to_lineno_entry> >
 197   Lineno_map;
 198
 199   Lineno_map line_number_map_;
 200 };
 201
 202 } // End namespace gold.
 203
 204 #endif // !defined(GOLD_DWARF_READER_H)