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      1 //===-- lib/MC/Disassembler.cpp - Disassembler Public C Interface ---------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #include "Disassembler.h"
     11 #include "llvm-c/Disassembler.h"
     12 
     13 #include "llvm/MC/MCAsmInfo.h"
     14 #include "llvm/MC/MCContext.h"
     15 #include "llvm/MC/MCDisassembler.h"
     16 #include "llvm/MC/MCInst.h"
     17 #include "llvm/MC/MCInstPrinter.h"
     18 #include "llvm/MC/MCRegisterInfo.h"
     19 #include "llvm/Support/MemoryObject.h"
     20 #include "llvm/Support/TargetRegistry.h"
     21 #include "llvm/Support/TargetSelect.h"
     22 
     23 namespace llvm {
     24 class Target;
     25 } // namespace llvm
     26 using namespace llvm;
     27 
     28 // LLVMCreateDisasm() creates a disassembler for the TripleName.  Symbolic
     29 // disassembly is supported by passing a block of information in the DisInfo
     30 // parameter and specifying the TagType and callback functions as described in
     31 // the header llvm-c/Disassembler.h .  The pointer to the block and the
     32 // functions can all be passed as NULL.  If successful, this returns a
     33 // disassembler context.  If not, it returns NULL.
     34 //
     35 LLVMDisasmContextRef LLVMCreateDisasm(const char *TripleName, void *DisInfo,
     36                                       int TagType, LLVMOpInfoCallback GetOpInfo,
     37                                       LLVMSymbolLookupCallback SymbolLookUp) {
     38   // Initialize targets and assembly printers/parsers.
     39   llvm::InitializeAllTargetInfos();
     40   llvm::InitializeAllTargetMCs();
     41   llvm::InitializeAllAsmParsers();
     42   llvm::InitializeAllDisassemblers();
     43 
     44   // Get the target.
     45   std::string Error;
     46   const Target *TheTarget = TargetRegistry::lookupTarget(TripleName, Error);
     47   assert(TheTarget && "Unable to create target!");
     48 
     49   // Get the assembler info needed to setup the MCContext.
     50   const MCAsmInfo *MAI = TheTarget->createMCAsmInfo(TripleName);
     51   assert(MAI && "Unable to create target asm info!");
     52 
     53   const MCRegisterInfo *MRI = TheTarget->createMCRegInfo(TripleName);
     54   assert(MRI && "Unable to create target register info!");
     55 
     56   // Package up features to be passed to target/subtarget
     57   std::string FeaturesStr;
     58   std::string CPU;
     59 
     60   const MCSubtargetInfo *STI = TheTarget->createMCSubtargetInfo(TripleName, CPU,
     61                                                                 FeaturesStr);
     62   assert(STI && "Unable to create subtarget info!");
     63 
     64   // Set up the MCContext for creating symbols and MCExpr's.
     65   MCContext *Ctx = new MCContext(*MAI, *MRI, 0);
     66   assert(Ctx && "Unable to create MCContext!");
     67 
     68   // Set up disassembler.
     69   MCDisassembler *DisAsm = TheTarget->createMCDisassembler(*STI);
     70   assert(DisAsm && "Unable to create disassembler!");
     71   DisAsm->setupForSymbolicDisassembly(GetOpInfo, SymbolLookUp, DisInfo, Ctx);
     72 
     73   // Set up the instruction printer.
     74   int AsmPrinterVariant = MAI->getAssemblerDialect();
     75   MCInstPrinter *IP = TheTarget->createMCInstPrinter(AsmPrinterVariant,
     76                                                      *MAI, *STI);
     77   assert(IP && "Unable to create instruction printer!");
     78 
     79   LLVMDisasmContext *DC = new LLVMDisasmContext(TripleName, DisInfo, TagType,
     80                                                 GetOpInfo, SymbolLookUp,
     81                                                 TheTarget, MAI, MRI,
     82                                                 Ctx, DisAsm, IP);
     83   assert(DC && "Allocation failure!");
     84 
     85   return DC;
     86 }
     87 
     88 //
     89 // LLVMDisasmDispose() disposes of the disassembler specified by the context.
     90 //
     91 void LLVMDisasmDispose(LLVMDisasmContextRef DCR){
     92   LLVMDisasmContext *DC = (LLVMDisasmContext *)DCR;
     93   delete DC;
     94 }
     95 
     96 namespace {
     97 //
     98 // The memory object created by LLVMDisasmInstruction().
     99 //
    100 class DisasmMemoryObject : public MemoryObject {
    101   uint8_t *Bytes;
    102   uint64_t Size;
    103   uint64_t BasePC;
    104 public:
    105   DisasmMemoryObject(uint8_t *bytes, uint64_t size, uint64_t basePC) :
    106                      Bytes(bytes), Size(size), BasePC(basePC) {}
    107 
    108   uint64_t getBase() const { return BasePC; }
    109   uint64_t getExtent() const { return Size; }
    110 
    111   int readByte(uint64_t Addr, uint8_t *Byte) const {
    112     if (Addr - BasePC >= Size)
    113       return -1;
    114     *Byte = Bytes[Addr - BasePC];
    115     return 0;
    116   }
    117 };
    118 } // end anonymous namespace
    119 
    120 //
    121 // LLVMDisasmInstruction() disassembles a single instruction using the
    122 // disassembler context specified in the parameter DC.  The bytes of the
    123 // instruction are specified in the parameter Bytes, and contains at least
    124 // BytesSize number of bytes.  The instruction is at the address specified by
    125 // the PC parameter.  If a valid instruction can be disassembled its string is
    126 // returned indirectly in OutString which whos size is specified in the
    127 // parameter OutStringSize.  This function returns the number of bytes in the
    128 // instruction or zero if there was no valid instruction.  If this function
    129 // returns zero the caller will have to pick how many bytes they want to step
    130 // over by printing a .byte, .long etc. to continue.
    131 //
    132 size_t LLVMDisasmInstruction(LLVMDisasmContextRef DCR, uint8_t *Bytes,
    133                              uint64_t BytesSize, uint64_t PC, char *OutString,
    134                              size_t OutStringSize){
    135   LLVMDisasmContext *DC = (LLVMDisasmContext *)DCR;
    136   // Wrap the pointer to the Bytes, BytesSize and PC in a MemoryObject.
    137   DisasmMemoryObject MemoryObject(Bytes, BytesSize, PC);
    138 
    139   uint64_t Size;
    140   MCInst Inst;
    141   const MCDisassembler *DisAsm = DC->getDisAsm();
    142   MCInstPrinter *IP = DC->getIP();
    143   MCDisassembler::DecodeStatus S;
    144   S = DisAsm->getInstruction(Inst, Size, MemoryObject, PC,
    145                              /*REMOVE*/ nulls(), DC->CommentStream);
    146   switch (S) {
    147   case MCDisassembler::Fail:
    148   case MCDisassembler::SoftFail:
    149     // FIXME: Do something different for soft failure modes?
    150     return 0;
    151 
    152   case MCDisassembler::Success: {
    153     DC->CommentStream.flush();
    154     StringRef Comments = DC->CommentsToEmit.str();
    155 
    156     SmallVector<char, 64> InsnStr;
    157     raw_svector_ostream OS(InsnStr);
    158     IP->printInst(&Inst, OS, Comments);
    159     OS.flush();
    160 
    161     // Tell the comment stream that the vector changed underneath it.
    162     DC->CommentsToEmit.clear();
    163     DC->CommentStream.resync();
    164 
    165     assert(OutStringSize != 0 && "Output buffer cannot be zero size");
    166     size_t OutputSize = std::min(OutStringSize-1, InsnStr.size());
    167     std::memcpy(OutString, InsnStr.data(), OutputSize);
    168     OutString[OutputSize] = '\0'; // Terminate string.
    169 
    170     return Size;
    171   }
    172   }
    173   return 0;
    174 }
    175