courgette/disassembler.h

   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
  12 // COURGETTE_HISTOGRAM_TARGETS prints out a histogram of how frequently
  13 // different target addresses are referenced.  Purely for debugging.
  14 #define COURGETTE_HISTOGRAM_TARGETS 0
  15
  16 namespace courgette {
  17
  18 class AssemblyProgram;
  19
  20 // A Relative Virtual Address is the address in the image file after it is
  21 // loaded into memory relative to the image load address.
  22 typedef uint32 RVA;
  23
  24 class Disassembler {
  25  public:
  26   virtual ~Disassembler();
  27
  28   virtual ExecutableType kind() { return EXE_UNKNOWN; }
  29
  30   // ok() may always be called but returns 'true' only after ParseHeader
  31   // succeeds.
  32   bool ok() const { return failure_reason_ == NULL; }
  33
  34   // Returns 'true' if the buffer appears to be a valid executable of the
  35   // expected type. It is not required that this be called before Disassemble.
  36   virtual bool ParseHeader() = 0;
  37
  38   // Disassembles the item passed to the factory method into the output
  39   // parameter 'program'.
  40   virtual bool Disassemble(AssemblyProgram* program) = 0;
  41
  42   // Returns the length of the source executable. May reduce after ParseHeader.
  43   size_t length() const { return length_; }
  44   const uint8* start() const { return start_; }
  45   const uint8* end() const { return end_; }
  46
  47   // Returns a pointer into the memory copy of the file format.
  48   // FileOffsetToPointer(0) returns a pointer to the start of the file format.
  49   const uint8* OffsetToPointer(size_t offset) const;
  50
  51  protected:
  52   Disassembler(const void* start, size_t length);
  53
  54   bool Good();
  55   bool Bad(const char *reason);
  56
  57   // Returns true if the array lies within our memory region.
  58   bool IsArrayInBounds(size_t offset, size_t elements, size_t element_size) {
  59     return offset <= length() && elements <= (length() - offset) / element_size;
  60   }
  61
  62   // These helper functions avoid the need for casts in the main code.
  63   uint16 ReadU16(const uint8* address, size_t offset) {
  64     return *reinterpret_cast<const uint16*>(address + offset);
  65   }
  66
  67   uint32 ReadU32(const uint8* address, size_t offset) {
  68     return *reinterpret_cast<const uint32*>(address + offset);
  69   }
  70
  71   uint64 ReadU64(const uint8* address, size_t offset) {
  72     return *reinterpret_cast<const uint64*>(address + offset);
  73   }
  74
  75   static uint32 Read32LittleEndian(const void* address) {
  76     return *reinterpret_cast<const uint32*>(address);
  77   }
  78
  79   static uint64 Read64LittleEndian(const void* address) {
  80     return *reinterpret_cast<const uint64*>(address);
  81   }
  82
  83   static uint16 Read16LittleEndian(const void* address) {
  84     return *reinterpret_cast<const uint16*>(address);
  85   }
  86
  87   // Reduce the length of the image in memory. Does not actually free
  88   // (or realloc) any memory. Usually only called via ParseHeader()
  89   void ReduceLength(size_t reduced_length);
  90
  91  private:
  92   const char* failure_reason_;
  93
  94   //
  95   // Basic information that is always valid after Construction, though
  96   // ParseHeader may shorten the length if the executable is shorter than
  97   // the total data.
  98   //
  99   size_t length_;         // In current memory.
 100   const uint8* start_;    // In current memory, base for 'file offsets'.
 101   const uint8* end_;      // In current memory.
 102
 103   DISALLOW_COPY_AND_ASSIGN(Disassembler);
 104 };
 105
 106 }  // namespace courgette
 107 #endif  // COURGETTE_DISASSEMBLER_H_