gold/dwarf_reader.h

   1 // dwarf_reader.h -- parse dwarf2/3 debug information for gold  -*- C++ -*-
   2
   3 // Copyright 2007, 2008, 2009, 2010 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
  50   // When we add entries to the table, we always use the last entry
  51   // with a given offset.  Given proper DWARF info, this should ensure
  52   // that the offset is a sufficient sort key.
  53   bool operator<(const Offset_to_lineno_entry& that) const
  54   { return this->offset < that.offset; }
  55 };
  56
  57 // This class is used to read the line information from the debugging
  58 // section of an object file.
  59
  60 class Dwarf_line_info
  61 {
  62  public:
  63   Dwarf_line_info()
  64   { }
  65
  66   virtual
  67   ~Dwarf_line_info()
  68   { }
  69
  70   // Given a section number and an offset, returns the associated
  71   // file and line-number, as a string: "file:lineno".  If unable
  72   // to do the mapping, returns the empty string.  You must call
  73   // read_line_mappings() before calling this function.
  74   std::string
  75   addr2line(unsigned int shndx, off_t offset)
  76   { return do_addr2line(shndx, offset); }
  77
  78   // A helper function for a single addr2line lookup.  It also keeps a
  79   // cache of the last CACHE_SIZE Dwarf_line_info objects it created;
  80   // set to 0 not to cache at all.  The larger CACHE_SIZE is, the more
  81   // chance this routine won't have to re-create a Dwarf_line_info
  82   // object for its addr2line computation; such creations are slow.
  83   // NOTE: Not thread-safe, so only call from one thread at a time.
  84   static std::string
  85   one_addr2line(Object* object, unsigned int shndx, off_t offset,
  86                 size_t cache_size);
  87
  88   // This reclaims all the memory that one_addr2line may have cached.
  89   // Use this when you know you will not be calling one_addr2line again.
  90   static void
  91   clear_addr2line_cache();
  92
  93  private:
  94   virtual std::string
  95   do_addr2line(unsigned int shndx, off_t offset) = 0;
  96 };
  97
  98 template<int size, bool big_endian>
  99 class Sized_dwarf_line_info : public Dwarf_line_info
 100 {
 101  public:
 102   // Initializes a .debug_line reader for a given object file.
 103   // If SHNDX is specified and non-negative, only read the debug
 104   // information that pertains to the specified section.
 105   Sized_dwarf_line_info(Object* object, unsigned int read_shndx = -1U);
 106
 107  private:
 108   std::string
 109   do_addr2line(unsigned int shndx, off_t offset);
 110
 111   // Start processing line info, and populates the offset_map_.
 112   // If SHNDX is non-negative, only store debug information that
 113   // pertains to the specified section.
 114   void
 115   read_line_mappings(Object*, unsigned int shndx);
 116
 117   // Reads the relocation section associated with .debug_line and
 118   // stores relocation information in reloc_map_.
 119   void
 120   read_relocs(Object*);
 121
 122   // Looks in the symtab to see what section a symbol is in.
 123   unsigned int
 124   symbol_section(Object*, unsigned int sym,
 125                  typename elfcpp::Elf_types<size>::Elf_Addr* value,
 126                  bool* is_ordinary);
 127
 128   // Reads the DWARF2/3 header for this line info.  Each takes as input
 129   // a starting buffer position, and returns the ending position.
 130   const unsigned char*
 131   read_header_prolog(const unsigned char* lineptr);
 132
 133   const unsigned char*
 134   read_header_tables(const unsigned char* lineptr);
 135
 136   // Reads the DWARF2/3 line information.  If shndx is non-negative,
 137   // discard all line information that doesn't pertain to the given
 138   // section.
 139   const unsigned char*
 140   read_lines(const unsigned char* lineptr, unsigned int shndx);
 141
 142   // Process a single line info opcode at START using the state
 143   // machine at LSM.  Return true if we should define a line using the
 144   // current state of the line state machine.  Place the length of the
 145   // opcode in LEN.
 146   bool
 147   process_one_opcode(const unsigned char* start,
 148                      struct LineStateMachine* lsm, size_t* len);
 149
 150   // Some parts of processing differ depending on whether the input
 151   // was a .o file or not.
 152   bool input_is_relobj();
 153
 154   // If we saw anything amiss while parsing, we set this to false.
 155   // Then addr2line will always fail (rather than return possibly-
 156   // corrupt data).
 157   bool data_valid_;
 158
 159   // A DWARF2/3 line info header.  This is not the same size as in the
 160   // actual file, as the one in the file may have a 32 bit or 64 bit
 161   // lengths.
 162
 163   struct Dwarf_line_infoHeader
 164   {
 165     off_t total_length;
 166     int version;
 167     off_t prologue_length;
 168     int min_insn_length; // insn stands for instructin
 169     bool default_is_stmt; // stmt stands for statement
 170     signed char line_base;
 171     int line_range;
 172     unsigned char opcode_base;
 173     std::vector<unsigned char> std_opcode_lengths;
 174     int offset_size;
 175   } header_;
 176
 177   // buffer is the buffer for our line info, starting at exactly where
 178   // the line info to read is.
 179   const unsigned char* buffer_;
 180   const unsigned char* buffer_end_;
 181
 182   // This has relocations that point into buffer.
 183   Track_relocs<size, big_endian> track_relocs_;
 184   // The type of the reloc section in track_relocs_--SHT_REL or SHT_RELA.
 185   unsigned int track_relocs_type_;
 186
 187   // This is used to figure out what section to apply a relocation to.
 188   const unsigned char* symtab_buffer_;
 189   section_size_type symtab_buffer_size_;
 190
 191   // Holds the directories and files as we see them.  We have an array
 192   // of directory-lists, one for each .o file we're reading (usually
 193   // there will just be one, but there may be more if input is a .so).
 194   std::vector<std::vector<std::string> > directories_;
 195   // The first part is an index into directories_, the second the filename.
 196   std::vector<std::vector< std::pair<int, std::string> > > files_;
 197
 198   // An index into the current directories_ and files_ vectors.
 199   int current_header_index_;
 200
 201   // A sorted map from offset of the relocation target to the shndx
 202   // and addend for the relocation.
 203   typedef std::map<typename elfcpp::Elf_types<size>::Elf_Addr,
 204                    std::pair<unsigned int,
 205                              typename elfcpp::Elf_types<size>::Elf_Swxword> >
 206   Reloc_map;
 207   Reloc_map reloc_map_;
 208
 209   // We have a vector of offset->lineno entries for every input section.
 210   typedef Unordered_map<unsigned int, std::vector<Offset_to_lineno_entry> >
 211   Lineno_map;
 212
 213   Lineno_map line_number_map_;
 214 };
 215
 216 } // End namespace gold.
 217
 218 #endif // !defined(GOLD_DWARF_READER_H)