1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef COURGETTE_DISASSEMBLER_H_
6#define COURGETTE_DISASSEMBLER_H_
7
8#include "base/basictypes.h"
9
10#include "courgette/courgette.h"
11
12namespace courgette {
13
14class AssemblyProgram;
15
16// A Relative Virtual Address is the address in the image file after it is
17// loaded into memory relative to the image load address.
18typedef uint32 RVA;
19
20class Disassembler {
21 public:
22  virtual ~Disassembler();
23
24  virtual ExecutableType kind() { return EXE_UNKNOWN; }
25
26  // ok() may always be called but returns 'true' only after ParseHeader
27  // succeeds.
28  bool ok() const { return failure_reason_ == NULL; }
29
30  // Returns 'true' if the buffer appears to be a valid executable of the
31  // expected type. It is not required that this be called before Disassemble.
32  virtual bool ParseHeader() = 0;
33
34  // Disassembles the item passed to the factory method into the output
35  // parameter 'program'.
36  virtual bool Disassemble(AssemblyProgram* program) = 0;
37
38  // Returns the length of the source executable. May reduce after ParseHeader.
39  size_t length() const { return length_; }
40  const uint8* start() const { return start_; }
41  const uint8* end() const { return end_; }
42
43  // Returns a pointer into the memory copy of the file format.
44  // FileOffsetToPointer(0) returns a pointer to the start of the file format.
45  const uint8* OffsetToPointer(size_t offset) const;
46
47 protected:
48  Disassembler(const void* start, size_t length);
49
50  bool Good();
51  bool Bad(const char *reason);
52
53  // These helper functions avoid the need for casts in the main code.
54  uint16 ReadU16(const uint8* address, size_t offset) {
55    return *reinterpret_cast<const uint16*>(address + offset);
56  }
57
58  uint32 ReadU32(const uint8* address, size_t offset) {
59    return *reinterpret_cast<const uint32*>(address + offset);
60  }
61
62  uint64 ReadU64(const uint8* address, size_t offset) {
63    return *reinterpret_cast<const uint64*>(address + offset);
64  }
65
66  static uint32 Read32LittleEndian(const void* address) {
67    return *reinterpret_cast<const uint32*>(address);
68  }
69
70  static uint16 Read16LittleEndian(const void* address) {
71    return *reinterpret_cast<const uint16*>(address);
72  }
73
74  // Reduce the length of the image in memory. Does not actually free
75  // (or realloc) any memory. Usually only called via ParseHeader()
76  void ReduceLength(size_t reduced_length);
77
78 private:
79  const char* failure_reason_;
80
81  //
82  // Basic information that is always valid after Construction, though
83  // ParseHeader may shorten the length if the executable is shorter than
84  // the total data.
85  //
86  size_t length_;         // In current memory.
87  const uint8* start_;    // In current memory, base for 'file offsets'.
88  const uint8* end_;      // In current memory.
89
90  DISALLOW_COPY_AND_ASSIGN(Disassembler);
91};
92
93}  // namespace courgette
94#endif  // COURGETTE_DISASSEMBLER_H_
95