path: root/gold/dwarf_reader.h

// 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)