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

// Copyright 2007, 2008, 2009, 2010 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 <map>

#include <limits.h>

#include "elfcpp.h"

#include "elfcpp_swap.h"

#include "dwarf.h"

#include "reloc.h"

namespace gold

{

template<int size, bool big_endian>

class Track_relocs;

struct LineStateMachine;

// 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 header_num;  // which file-list to use (i.e. which .o file are we in)

  // A pointer into files_.

  unsigned int file_num : sizeof(int) * CHAR_BIT - 1;

  // True if this was the last entry for the current offset, meaning

  // it's the line that actually applies.

  unsigned int last_line_for_offset : 1;

  // The line number in the source file.  -1 to indicate end-of-function.

  int line_num;

  // This sorts by offsets first, and then puts the correct line to

  // report for a given offset at the beginning of the run of equal

  // offsets (so that asking for 1 line gives the best answer).  This

  // is not a total ordering.

  bool operator<(const Offset_to_lineno_entry& that) const

  {

    if (this->offset != that.offset)

      return this->offset < that.offset;

    // Note the '>' which makes this sort 'true' first.

    return this->last_line_for_offset > that.last_line_for_offset;

  }

};

// This class is used to read the line information from the debugging

// section of an object file.

class Dwarf_line_info

{

 public:

  Dwarf_line_info()

  { }

  virtual

  ~Dwarf_line_info()

  { }

  // 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.  If

  // 'other_lines' is non-NULL, fills that in with other line

  // numbers assigned to the same offset.

  std::string

  addr2line(unsigned int shndx, off_t offset,

            std::vector<std::string>* other_lines)

  { return this->do_addr2line(shndx, offset, other_lines); }

  // A helper function for a single addr2line lookup.  It also keeps a

  // cache of the last CACHE_SIZE Dwarf_line_info objects it created;

  // set to 0 not to cache at all.  The larger CACHE_SIZE is, the more

  // chance this routine won't have to re-create a Dwarf_line_info

  // object for its addr2line computation; such creations are slow.

  // NOTE: Not thread-safe, so only call from one thread at a time.

  static std::string

  one_addr2line(Object* object, unsigned int shndx, off_t offset,

                size_t cache_size, std::vector<std::string>* other_lines);

  // This reclaims all the memory that one_addr2line may have cached.

  // Use this when you know you will not be calling one_addr2line again.

  static void

  clear_addr2line_cache();

 private:

  virtual std::string

  do_addr2line(unsigned int shndx, off_t offset,

               std::vector<std::string>* other_lines) = 0;

};

template<int size, bool big_endian>

class Sized_dwarf_line_info : public Dwarf_line_info

{

 public:

  // Initializes a .debug_line reader for a given object file.

  // If SHNDX is specified and non-negative, only read the debug

  // information that pertains to the specified section.

  Sized_dwarf_line_info(Object* object, unsigned int read_shndx = -1U);

  virtual

  ~Sized_dwarf_line_info()

  {

    if (this->buffer_start_ != NULL)

      delete[] this->buffer_start_;

  }

 private:

  std::string

  do_addr2line(unsigned int shndx, off_t offset,

               std::vector<std::string>* other_lines);

  // Formats a file and line number to a string like "dirname/filename:lineno".

  std::string

  format_file_lineno(const Offset_to_lineno_entry& lineno) const;

  // Start processing line info, and populates the offset_map_.

  // If SHNDX is non-negative, only store debug information that

  // pertains to the specified section.

  void

  read_line_mappings(Object*, unsigned int shndx);

  // Reads the relocation section associated with .debug_line and

  // stores relocation information in reloc_map_.

  void

  read_relocs(Object*);

  // Looks in the symtab to see what section a symbol is in.

  unsigned int

  symbol_section(Object*, unsigned int sym,

                 typename elfcpp::Elf_types<size>::Elf_Addr* value,

                 bool* is_ordinary);

  // Reads the DWARF2/3 header for this line info.  Each takes as input

  // a starting buffer position, and returns the ending position.

  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.  If shndx is non-negative,

  // discard all line information that doesn't pertain to the given

  // section.

  const unsigned char*

  read_lines(const unsigned char* lineptr, unsigned int shndx);

  // 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(const unsigned char* start,

                     struct LineStateMachine* lsm, size_t* len);

  // Some parts of processing differ depending on whether the input

  // was a .o file or not.

  bool input_is_relobj();

  // If we saw anything amiss while parsing, we set this to false.

  // Then addr2line will always fail (rather than return possibly-

  // corrupt data).

  bool data_valid_;

  // 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* buffer_end_;

  // If the buffer was allocated temporarily, and therefore must be

  // deallocated in the dtor, this contains a pointer to the start

  // of the buffer.

  const unsigned char* buffer_start_;

  // This has relocations that point into buffer.

  Track_relocs<size, big_endian> track_relocs_;

  // The type of the reloc section in track_relocs_--SHT_REL or SHT_RELA.

  unsigned int track_relocs_type_;

  // This is used to figure out what section to apply a relocation to.

  const unsigned char* symtab_buffer_;

  section_size_type symtab_buffer_size_;

  // Holds the directories and files as we see them.  We have an array

  // of directory-lists, one for each .o file we're reading (usually

  // there will just be one, but there may be more if input is a .so).

  std::vector<std::vector<std::string> > directories_;

  // The first part is an index into directories_, the second the filename.

  std::vector<std::vector< std::pair<int, std::string> > > files_;

  // An index into the current directories_ and files_ vectors.

  int current_header_index_;

  // A sorted map from offset of the relocation target to the shndx

  // and addend for the relocation.

  typedef std::map<typename elfcpp::Elf_types<size>::Elf_Addr,

                   std::pair<unsigned int,

                             typename elfcpp::Elf_types<size>::Elf_Swxword> >

  Reloc_map;

  Reloc_map reloc_map_;

  // 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)