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   // These helper functions avoid the need for casts in the main code.
  58   uint16 ReadU16(const uint8* address, size_t offset) {
  59     return *reinterpret_cast<const uint16*>(address + offset);
  60   }
  61
  62   uint32 ReadU32(const uint8* address, size_t offset) {
  63     return *reinterpret_cast<const uint32*>(address + offset);
  64   }
  65
  66   uint64 ReadU64(const uint8* address, size_t offset) {
  67     return *reinterpret_cast<const uint64*>(address + offset);
  68   }
  69
  70   static uint32 Read32LittleEndian(const void* address) {
  71     return *reinterpret_cast<const uint32*>(address);
  72   }
  73
  74   static uint16 Read16LittleEndian(const void* address) {
  75     return *reinterpret_cast<const uint16*>(address);
  76   }
  77
  78   // Reduce the length of the image in memory. Does not actually free
  79   // (or realloc) any memory. Usually only called via ParseHeader()
  80   void ReduceLength(size_t reduced_length);
  81
  82  private:
  83   const char* failure_reason_;
  84
  85   //
  86   // Basic information that is always valid after Construction, though
  87   // ParseHeader may shorten the length if the executable is shorter than
  88   // the total data.
  89   //
  90   size_t length_;         // In current memory.
  91   const uint8* start_;    // In current memory, base for 'file offsets'.
  92   const uint8* end_;      // In current memory.
  93
  94   DISALLOW_COPY_AND_ASSIGN(Disassembler);
  95 };
  96
  97 }  // namespace courgette
  98 #endif  // COURGETTE_DISASSEMBLER_H_