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 #include <limits.h>
  29
  30 #include "elfcpp.h"
  31 #include "elfcpp_swap.h"
  32 #include "dwarf.h"
  33 #include "reloc.h"
  34
  35 namespace gold
  36 {
  37
  38 template<int size, bool big_endian>
  39 class Track_relocs;
  40 struct LineStateMachine;
  41
  42 // We can't do better than to keep the offsets in a sorted vector.
  43 // Here, offset is the key, and file_num/line_num is the value.
  44 struct Offset_to_lineno_entry
  45 {
  46   off_t offset;
  47   int header_num;  // which file-list to use (i.e. which .o file are we in)
  48   // A pointer into files_.
  49   unsigned int file_num : sizeof(int) * CHAR_BIT - 1;
  50   // True if this was the last entry for the current offset, meaning
  51   // it's the line that actually applies.
  52   unsigned int last_line_for_offset : 1;
  53   // The line number in the source file.  -1 to indicate end-of-function.
  54   int line_num;
  55
  56   // This sorts by offsets first, and then puts the correct line to
  57   // report for a given offset at the beginning of the run of equal
  58   // offsets (so that asking for 1 line gives the best answer).  This
  59   // is not a total ordering.
  60   bool operator<(const Offset_to_lineno_entry& that) const
  61   {
  62     if (this->offset != that.offset)
  63       return this->offset < that.offset;
  64     // Note the '>' which makes this sort 'true' first.
  65     return this->last_line_for_offset > that.last_line_for_offset;
  66   }
  67 };
  68
  69 // This class is used to read the line information from the debugging
  70 // section of an object file.
  71
  72 class Dwarf_line_info
  73 {
  74  public:
  75   Dwarf_line_info()
  76   { }
  77
  78   virtual
  79   ~Dwarf_line_info()
  80   { }
  81
  82   // Given a section number and an offset, returns the associated
  83   // file and line-number, as a string: "file:lineno".  If unable
  84   // to do the mapping, returns the empty string.  You must call
  85   // read_line_mappings() before calling this function.  If
  86   // 'other_lines' is non-NULL, fills that in with other line
  87   // numbers assigned to the same offset.
  88   std::string
  89   addr2line(unsigned int shndx, off_t offset,
  90             std::vector<std::string>* other_lines)
  91   { return this->do_addr2line(shndx, offset, other_lines); }
  92
  93   // A helper function for a single addr2line lookup.  It also keeps a
  94   // cache of the last CACHE_SIZE Dwarf_line_info objects it created;
  95   // set to 0 not to cache at all.  The larger CACHE_SIZE is, the more
  96   // chance this routine won't have to re-create a Dwarf_line_info
  97   // object for its addr2line computation; such creations are slow.
  98   // NOTE: Not thread-safe, so only call from one thread at a time.
  99   static std::string
 100   one_addr2line(Object* object, unsigned int shndx, off_t offset,
 101                 size_t cache_size, std::vector<std::string>* other_lines);
 102
 103   // This reclaims all the memory that one_addr2line may have cached.
 104   // Use this when you know you will not be calling one_addr2line again.
 105   static void
 106   clear_addr2line_cache();
 107
 108  private:
 109   virtual std::string
 110   do_addr2line(unsigned int shndx, off_t offset,
 111                std::vector<std::string>* other_lines) = 0;
 112 };
 113
 114 template<int size, bool big_endian>
 115 class Sized_dwarf_line_info : public Dwarf_line_info
 116 {
 117  public:
 118   // Initializes a .debug_line reader for a given object file.
 119   // If SHNDX is specified and non-negative, only read the debug
 120   // information that pertains to the specified section.
 121   Sized_dwarf_line_info(Object* object, unsigned int read_shndx = -1U);
 122
 123  private:
 124   std::string
 125   do_addr2line(unsigned int shndx, off_t offset,
 126                std::vector<std::string>* other_lines);
 127
 128   // Formats a file and line number to a string like "dirname/filename:lineno".
 129   std::string
 130   format_file_lineno(const Offset_to_lineno_entry& lineno) const;
 131
 132   // Start processing line info, and populates the offset_map_.
 133   // If SHNDX is non-negative, only store debug information that
 134   // pertains to the specified section.
 135   void
 136   read_line_mappings(Object*, unsigned int shndx);
 137
 138   // Reads the relocation section associated with .debug_line and
 139   // stores relocation information in reloc_map_.
 140   void
 141   read_relocs(Object*);
 142
 143   // Looks in the symtab to see what section a symbol is in.
 144   unsigned int
 145   symbol_section(Object*, unsigned int sym,
 146                  typename elfcpp::Elf_types<size>::Elf_Addr* value,
 147                  bool* is_ordinary);
 148
 149   // Reads the DWARF2/3 header for this line info.  Each takes as input
 150   // a starting buffer position, and returns the ending position.
 151   const unsigned char*
 152   read_header_prolog(const unsigned char* lineptr);
 153
 154   const unsigned char*
 155   read_header_tables(const unsigned char* lineptr);
 156
 157   // Reads the DWARF2/3 line information.  If shndx is non-negative,
 158   // discard all line information that doesn't pertain to the given
 159   // section.
 160   const unsigned char*
 161   read_lines(const unsigned char* lineptr, unsigned int shndx);
 162
 163   // Process a single line info opcode at START using the state
 164   // machine at LSM.  Return true if we should define a line using the
 165   // current state of the line state machine.  Place the length of the
 166   // opcode in LEN.
 167   bool
 168   process_one_opcode(const unsigned char* start,
 169                      struct LineStateMachine* lsm, size_t* len);
 170
 171   // Some parts of processing differ depending on whether the input
 172   // was a .o file or not.
 173   bool input_is_relobj();
 174
 175   // If we saw anything amiss while parsing, we set this to false.
 176   // Then addr2line will always fail (rather than return possibly-
 177   // corrupt data).
 178   bool data_valid_;
 179
 180   // A DWARF2/3 line info header.  This is not the same size as in the
 181   // actual file, as the one in the file may have a 32 bit or 64 bit
 182   // lengths.
 183
 184   struct Dwarf_line_infoHeader
 185   {
 186     off_t total_length;
 187     int version;
 188     off_t prologue_length;
 189     int min_insn_length; // insn stands for instructin
 190     bool default_is_stmt; // stmt stands for statement
 191     signed char line_base;
 192     int line_range;
 193     unsigned char opcode_base;
 194     std::vector<unsigned char> std_opcode_lengths;
 195     int offset_size;
 196   } header_;
 197
 198   // buffer is the buffer for our line info, starting at exactly where
 199   // the line info to read is.
 200   const unsigned char* buffer_;
 201   const unsigned char* buffer_end_;
 202
 203   // This has relocations that point into buffer.
 204   Track_relocs<size, big_endian> track_relocs_;
 205   // The type of the reloc section in track_relocs_--SHT_REL or SHT_RELA.
 206   unsigned int track_relocs_type_;
 207
 208   // This is used to figure out what section to apply a relocation to.
 209   const unsigned char* symtab_buffer_;
 210   section_size_type symtab_buffer_size_;
 211
 212   // Holds the directories and files as we see them.  We have an array
 213   // of directory-lists, one for each .o file we're reading (usually
 214   // there will just be one, but there may be more if input is a .so).
 215   std::vector<std::vector<std::string> > directories_;
 216   // The first part is an index into directories_, the second the filename.
 217   std::vector<std::vector< std::pair<int, std::string> > > files_;
 218
 219   // An index into the current directories_ and files_ vectors.
 220   int current_header_index_;
 221
 222   // A sorted map from offset of the relocation target to the shndx
 223   // and addend for the relocation.
 224   typedef std::map<typename elfcpp::Elf_types<size>::Elf_Addr,
 225                    std::pair<unsigned int,
 226                              typename elfcpp::Elf_types<size>::Elf_Swxword> >
 227   Reloc_map;
 228   Reloc_map reloc_map_;
 229
 230   // We have a vector of offset->lineno entries for every input section.
 231   typedef Unordered_map<unsigned int, std::vector<Offset_to_lineno_entry> >
 232   Lineno_map;
 233
 234   Lineno_map line_number_map_;
 235 };
 236
 237 } // End namespace gold.
 238
 239 #endif // !defined(GOLD_DWARF_READER_H)