courgette/assembly_program.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_ASSEMBLY_PROGRAM_H_
   6 #define COURGETTE_ASSEMBLY_PROGRAM_H_
   7
   8 #include <map>
   9 #include <set>
  10 #include <vector>
  11
  12 #include "base/basictypes.h"
  13 #include "base/memory/scoped_ptr.h"
  14
  15 #include "courgette/disassembler.h"
  16 #include "courgette/memory_allocator.h"
  17
  18 namespace courgette {
  19
  20 class EncodedProgram;
  21 class Instruction;
  22
  23 typedef NoThrowBuffer<Instruction*> InstructionVector;
  24
  25 // A Label is a symbolic reference to an address.  Unlike a conventional
  26 // assembly language, we always know the address.  The address will later be
  27 // stored in a table and the Label will be replaced with the index into the
  28 // table.
  29 //
  30 // TODO(sra): Make fields private and add setters and getters.
  31 class Label {
  32  public:
  33   static const int kNoIndex = -1;
  34   Label() : rva_(0), index_(kNoIndex), count_(0) {}
  35   explicit Label(RVA rva) : rva_(rva), index_(kNoIndex), count_(0) {}
  36
  37   RVA rva_;    // Address referred to by the label.
  38   int index_;  // Index of address in address table, kNoIndex until assigned.
  39   int count_;
  40 };
  41
  42 typedef std::map<RVA, Label*> RVAToLabel;
  43
  44 // An AssemblyProgram is the result of disassembling an executable file.
  45 //
  46 // * The disassembler creates labels in the AssemblyProgram and emits
  47 //   'Instructions'.
  48 // * The disassembler then calls DefaultAssignIndexes to assign
  49 //   addresses to positions in the address tables.
  50 // * [Optional step]
  51 // * At this point the AssemblyProgram can be converted into an
  52 //   EncodedProgram and serialized to an output stream.
  53 // * Later, the EncodedProgram can be deserialized and assembled into
  54 //   the original file.
  55 //
  56 // The optional step is to modify the AssemblyProgram.  One form of modification
  57 // is to assign indexes in such a way as to make the EncodedProgram for this
  58 // AssemblyProgram look more like the EncodedProgram for some other
  59 // AssemblyProgram.  The modification process should call UnassignIndexes, do
  60 // its own assignment, and then call AssignRemainingIndexes to ensure all
  61 // indexes are assigned.
  62 //
  63 class AssemblyProgram {
  64  public:
  65   explicit AssemblyProgram(ExecutableType kind);
  66   ~AssemblyProgram();
  67
  68   ExecutableType kind() const { return kind_; }
  69
  70   void set_image_base(uint64 image_base) { image_base_ = image_base; }
  71
  72   // Instructions will be assembled in the order they are emitted.
  73
  74   // Generates an entire base relocation table.
  75   CheckBool EmitPeRelocsInstruction() WARN_UNUSED_RESULT;
  76
  77   // Generates an ELF style relocation table for X86.
  78   CheckBool EmitElfRelocationInstruction() WARN_UNUSED_RESULT;
  79
  80   // Generates an ELF style relocation table for ARM.
  81   CheckBool EmitElfARMRelocationInstruction() WARN_UNUSED_RESULT;
  82
  83   // Following instruction will be assembled at address 'rva'.
  84   CheckBool EmitOriginInstruction(RVA rva) WARN_UNUSED_RESULT;
  85
  86   // Generates a single byte of data or machine instruction.
  87   CheckBool EmitByteInstruction(uint8 byte) WARN_UNUSED_RESULT;
  88
  89   // Generates multiple bytes of data or machine instructions.
  90   CheckBool EmitBytesInstruction(const uint8* value, uint32 len)
  91       WARN_UNUSED_RESULT;
  92
  93   // Generates 4-byte relative reference to address of 'label'.
  94   CheckBool EmitRel32(Label* label) WARN_UNUSED_RESULT;
  95
  96   // Generates 4-byte relative reference to address of 'label' for
  97   // ARM.
  98   CheckBool EmitRel32ARM(uint16 op, Label* label, const uint8* arm_op,
  99                          uint16 op_size) WARN_UNUSED_RESULT;
 100
 101   // Generates 4-byte absolute reference to address of 'label'.
 102   CheckBool EmitAbs32(Label* label) WARN_UNUSED_RESULT;
 103
 104   // Looks up a label or creates a new one.  Might return NULL.
 105   Label* FindOrMakeAbs32Label(RVA rva);
 106
 107   // Looks up a label or creates a new one.  Might return NULL.
 108   Label* FindOrMakeRel32Label(RVA rva);
 109
 110   void DefaultAssignIndexes();
 111   void UnassignIndexes();
 112   void AssignRemainingIndexes();
 113
 114   EncodedProgram* Encode() const;
 115
 116   // Accessor for instruction list.
 117   const InstructionVector& instructions() const {
 118     return instructions_;
 119   }
 120
 121   // Returns the label if the instruction contains and absolute address,
 122   // otherwise returns NULL.
 123   Label* InstructionAbs32Label(const Instruction* instruction) const;
 124
 125   // Returns the label if the instruction contains and rel32 offset,
 126   // otherwise returns NULL.
 127   Label* InstructionRel32Label(const Instruction* instruction) const;
 128
 129   // Trim underused labels
 130   CheckBool TrimLabels();
 131
 132   void PrintLabelCounts(RVAToLabel* labels);
 133   void CountRel32ARM();
 134
 135  private:
 136   ExecutableType kind_;
 137
 138   CheckBool Emit(Instruction* instruction) WARN_UNUSED_RESULT;
 139
 140   static const int kLabelLowerLimit;
 141
 142   // Looks up a label or creates a new one.  Might return NULL.
 143   Label* FindLabel(RVA rva, RVAToLabel* labels);
 144
 145   // Helper methods for the public versions.
 146   static void UnassignIndexes(RVAToLabel* labels);
 147   static void DefaultAssignIndexes(RVAToLabel* labels);
 148   static void AssignRemainingIndexes(RVAToLabel* labels);
 149
 150   // Sharing instructions that emit a single byte saves a lot of space.
 151   Instruction* GetByteInstruction(uint8 byte);
 152   scoped_ptr<Instruction*[]> byte_instruction_cache_;
 153
 154   uint64 image_base_;  // Desired or mandated base address of image.
 155
 156   InstructionVector instructions_;  // All the instructions in program.
 157
 158   // These are lookup maps to find the label associated with a given address.
 159   // We have separate label spaces for addresses referenced by rel32 labels and
 160   // abs32 labels.  This is somewhat arbitrary.
 161   RVAToLabel rel32_labels_;
 162   RVAToLabel abs32_labels_;
 163
 164   DISALLOW_COPY_AND_ASSIGN(AssemblyProgram);
 165 };
 166
 167 }  // namespace courgette
 168 #endif  // COURGETTE_ASSEMBLY_PROGRAM_H_