1// dwarf_reader.h -- parse dwarf2/3 debug information for gold  -*- C++ -*-
2
3// Copyright 2007, 2008, 2009 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
34namespace gold
35{
36
37template<int size, bool big_endian>
38class Track_relocs;
39struct 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.
43struct 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
57class 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 also keeps a
76  // cache of the last CACHE_SIZE Dwarf_line_info objects it created;
77  // set to 0 not to cache at all.  The larger CACHE_SIZE is, the more
78  // chance this routine won't have to re-create a Dwarf_line_info
79  // object for its addr2line computation; such creations are slow.
80  // NOTE: Not thread-safe, so only call from one thread at a time.
81  static std::string
82  one_addr2line(Object* object, unsigned int shndx, off_t offset,
83                size_t cache_size);
84
85  // This reclaims all the memory that one_addr2line may have cached.
86  // Use this when you know you will not be calling one_addr2line again.
87  static void
88  clear_addr2line_cache();
89
90 private:
91  virtual std::string
92  do_addr2line(unsigned int shndx, off_t offset) = 0;
93};
94
95template<int size, bool big_endian>
96class Sized_dwarf_line_info : public Dwarf_line_info
97{
98 public:
99  // Initializes a .debug_line reader for a given object file.
100  // If SHNDX is specified and non-negative, only read the debug
101  // information that pertains to the specified section.
102  Sized_dwarf_line_info(Object* object, unsigned int read_shndx = -1U);
103
104 private:
105  std::string
106  do_addr2line(unsigned int shndx, off_t offset);
107
108  // Start processing line info, and populates the offset_map_.
109  // If SHNDX is non-negative, only store debug information that
110  // pertains to the specified section.
111  void
112  read_line_mappings(Object*, unsigned int shndx);
113
114  // Reads the relocation section associated with .debug_line and
115  // stores relocation information in reloc_map_.
116  void
117  read_relocs(Object*);
118
119  // Looks in the symtab to see what section a symbol is in.
120  unsigned int
121  symbol_section(Object*, unsigned int sym,
122                 typename elfcpp::Elf_types<size>::Elf_Addr* value,
123		 bool* is_ordinary);
124
125  // Reads the DWARF2/3 header for this line info.  Each takes as input
126  // a starting buffer position, and returns the ending position.
127  const unsigned char*
128  read_header_prolog(const unsigned char* lineptr);
129
130  const unsigned char*
131  read_header_tables(const unsigned char* lineptr);
132
133  // Reads the DWARF2/3 line information.  If shndx is non-negative,
134  // discard all line information that doesn't pertain to the given
135  // section.
136  const unsigned char*
137  read_lines(const unsigned char* lineptr, unsigned int shndx);
138
139  // Process a single line info opcode at START using the state
140  // machine at LSM.  Return true if we should define a line using the
141  // current state of the line state machine.  Place the length of the
142  // opcode in LEN.
143  bool
144  process_one_opcode(const unsigned char* start,
145                     struct LineStateMachine* lsm, size_t* len);
146
147  // Some parts of processing differ depending on whether the input
148  // was a .o file or not.
149  bool input_is_relobj();
150
151  // If we saw anything amiss while parsing, we set this to false.
152  // Then addr2line will always fail (rather than return possibly-
153  // corrupt data).
154  bool data_valid_;
155
156  // A DWARF2/3 line info header.  This is not the same size as in the
157  // actual file, as the one in the file may have a 32 bit or 64 bit
158  // lengths.
159
160  struct Dwarf_line_infoHeader
161  {
162    off_t total_length;
163    int version;
164    off_t prologue_length;
165    int min_insn_length; // insn stands for instructin
166    bool default_is_stmt; // stmt stands for statement
167    signed char line_base;
168    int line_range;
169    unsigned char opcode_base;
170    std::vector<unsigned char> std_opcode_lengths;
171    int offset_size;
172  } header_;
173
174  // buffer is the buffer for our line info, starting at exactly where
175  // the line info to read is.
176  const unsigned char* buffer_;
177  const unsigned char* buffer_end_;
178
179  // This has relocations that point into buffer.
180  Track_relocs<size, big_endian> track_relocs_;
181
182  // This is used to figure out what section to apply a relocation to.
183  const unsigned char* symtab_buffer_;
184  section_size_type symtab_buffer_size_;
185
186  // Holds the directories and files as we see them.  We have an array
187  // of directory-lists, one for each .o file we're reading (usually
188  // there will just be one, but there may be more if input is a .so).
189  std::vector<std::vector<std::string> > directories_;
190  // The first part is an index into directories_, the second the filename.
191  std::vector<std::vector< std::pair<int, std::string> > > files_;
192
193  // An index into the current directories_ and files_ vectors.
194  int current_header_index_;
195
196  // A sorted map from offset of the relocation target to the shndx
197  // and addend for the relocation.
198  typedef std::map<typename elfcpp::Elf_types<size>::Elf_Addr,
199                   std::pair<unsigned int,
200                             typename elfcpp::Elf_types<size>::Elf_Swxword> >
201  Reloc_map;
202  Reloc_map reloc_map_;
203
204  // We have a vector of offset->lineno entries for every input section.
205  typedef Unordered_map<unsigned int, std::vector<Offset_to_lineno_entry> >
206  Lineno_map;
207
208  Lineno_map line_number_map_;
209};
210
211} // End namespace gold.
212
213#endif // !defined(GOLD_DWARF_READER_H)
214