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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/MCInstrInfo.h"
     19 #include "llvm/MC/MCRegisterInfo.h"
     20 #include "llvm/MC/MCSubtargetInfo.h"
     21 #include "llvm/Support/MemoryObject.h"
     22 #include "llvm/Support/TargetRegistry.h"
     23 #include "llvm/Support/TargetSelect.h"
     24 #include "llvm/Support/ErrorHandling.h"
     25 
     26 namespace llvm {
     27 class Target;
     28 } // namespace llvm
     29 using namespace llvm;
     30 
     31 // LLVMCreateDisasm() creates a disassembler for the TripleName.  Symbolic
     32 // disassembly is supported by passing a block of information in the DisInfo
     33 // parameter and specifying the TagType and callback functions as described in
     34 // the header llvm-c/Disassembler.h .  The pointer to the block and the
     35 // functions can all be passed as NULL.  If successful, this returns a
     36 // disassembler context.  If not, it returns NULL.
     37 //
     38 LLVMDisasmContextRef LLVMCreateDisasm(const char *TripleName, void *DisInfo,
     39                                       int TagType, LLVMOpInfoCallback GetOpInfo,
     40                                       LLVMSymbolLookupCallback SymbolLookUp) {
     41   // Initialize targets and assembly printers/parsers.
     42   // FIXME: Clients are responsible for initializing the targets. And this
     43   // would be done by calling routines in "llvm-c/Target.h" which are static
     44   // line functions. But the current use of LLVMCreateDisasm() is to dynamically
     45   // load libLTO with dlopen() and then lookup the symbols using dlsym().
     46   // And since these initialize routines are static that does not work which
     47   // is why the call to them in this 'C' library API was added back.
     48   llvm::InitializeAllTargetInfos();
     49   llvm::InitializeAllTargetMCs();
     50   llvm::InitializeAllAsmParsers();
     51   llvm::InitializeAllDisassemblers();
     52 
     53   // Get the target.
     54   std::string Error;
     55   const Target *TheTarget = TargetRegistry::lookupTarget(TripleName, Error);
     56   assert(TheTarget && "Unable to create target!");
     57 
     58   // Get the assembler info needed to setup the MCContext.
     59   const MCAsmInfo *MAI = TheTarget->createMCAsmInfo(TripleName);
     60   assert(MAI && "Unable to create target asm info!");
     61 
     62   const MCInstrInfo *MII = TheTarget->createMCInstrInfo();
     63   assert(MII && "Unable to create target instruction info!");
     64 
     65   const MCRegisterInfo *MRI = TheTarget->createMCRegInfo(TripleName);
     66   assert(MRI && "Unable to create target register info!");
     67 
     68   // Package up features to be passed to target/subtarget
     69   std::string FeaturesStr;
     70   std::string CPU;
     71 
     72   const MCSubtargetInfo *STI = TheTarget->createMCSubtargetInfo(TripleName, CPU,
     73                                                                 FeaturesStr);
     74   assert(STI && "Unable to create subtarget info!");
     75 
     76   // Set up the MCContext for creating symbols and MCExpr's.
     77   MCContext *Ctx = new MCContext(*MAI, *MRI, 0);
     78   assert(Ctx && "Unable to create MCContext!");
     79 
     80   // Set up disassembler.
     81   MCDisassembler *DisAsm = TheTarget->createMCDisassembler(*STI);
     82   assert(DisAsm && "Unable to create disassembler!");
     83   DisAsm->setupForSymbolicDisassembly(GetOpInfo, SymbolLookUp, DisInfo, Ctx);
     84 
     85   // Set up the instruction printer.
     86   int AsmPrinterVariant = MAI->getAssemblerDialect();
     87   MCInstPrinter *IP = TheTarget->createMCInstPrinter(AsmPrinterVariant,
     88                                                      *MAI, *MII, *MRI, *STI);
     89   assert(IP && "Unable to create instruction printer!");
     90 
     91   LLVMDisasmContext *DC = new LLVMDisasmContext(TripleName, DisInfo, TagType,
     92                                                 GetOpInfo, SymbolLookUp,
     93                                                 TheTarget, MAI, MRI,
     94                                                 STI, MII, Ctx, DisAsm, IP);
     95   assert(DC && "Allocation failure!");
     96 
     97   return DC;
     98 }
     99 
    100 //
    101 // LLVMDisasmDispose() disposes of the disassembler specified by the context.
    102 //
    103 void LLVMDisasmDispose(LLVMDisasmContextRef DCR){
    104   LLVMDisasmContext *DC = (LLVMDisasmContext *)DCR;
    105   delete DC;
    106 }
    107 
    108 namespace {
    109 //
    110 // The memory object created by LLVMDisasmInstruction().
    111 //
    112 class DisasmMemoryObject : public MemoryObject {
    113   uint8_t *Bytes;
    114   uint64_t Size;
    115   uint64_t BasePC;
    116 public:
    117   DisasmMemoryObject(uint8_t *bytes, uint64_t size, uint64_t basePC) :
    118                      Bytes(bytes), Size(size), BasePC(basePC) {}
    119 
    120   uint64_t getBase() const { return BasePC; }
    121   uint64_t getExtent() const { return Size; }
    122 
    123   int readByte(uint64_t Addr, uint8_t *Byte) const {
    124     if (Addr - BasePC >= Size)
    125       return -1;
    126     *Byte = Bytes[Addr - BasePC];
    127     return 0;
    128   }
    129 };
    130 } // end anonymous namespace
    131 
    132 //
    133 // LLVMDisasmInstruction() disassembles a single instruction using the
    134 // disassembler context specified in the parameter DC.  The bytes of the
    135 // instruction are specified in the parameter Bytes, and contains at least
    136 // BytesSize number of bytes.  The instruction is at the address specified by
    137 // the PC parameter.  If a valid instruction can be disassembled its string is
    138 // returned indirectly in OutString which whos size is specified in the
    139 // parameter OutStringSize.  This function returns the number of bytes in the
    140 // instruction or zero if there was no valid instruction.  If this function
    141 // returns zero the caller will have to pick how many bytes they want to step
    142 // over by printing a .byte, .long etc. to continue.
    143 //
    144 size_t LLVMDisasmInstruction(LLVMDisasmContextRef DCR, uint8_t *Bytes,
    145                              uint64_t BytesSize, uint64_t PC, char *OutString,
    146                              size_t OutStringSize){
    147   LLVMDisasmContext *DC = (LLVMDisasmContext *)DCR;
    148   // Wrap the pointer to the Bytes, BytesSize and PC in a MemoryObject.
    149   DisasmMemoryObject MemoryObject(Bytes, BytesSize, PC);
    150 
    151   uint64_t Size;
    152   MCInst Inst;
    153   const MCDisassembler *DisAsm = DC->getDisAsm();
    154   MCInstPrinter *IP = DC->getIP();
    155   MCDisassembler::DecodeStatus S;
    156   S = DisAsm->getInstruction(Inst, Size, MemoryObject, PC,
    157                              /*REMOVE*/ nulls(), DC->CommentStream);
    158   switch (S) {
    159   case MCDisassembler::Fail:
    160   case MCDisassembler::SoftFail:
    161     // FIXME: Do something different for soft failure modes?
    162     return 0;
    163 
    164   case MCDisassembler::Success: {
    165     DC->CommentStream.flush();
    166     StringRef Comments = DC->CommentsToEmit.str();
    167 
    168     SmallVector<char, 64> InsnStr;
    169     raw_svector_ostream OS(InsnStr);
    170     IP->printInst(&Inst, OS, Comments);
    171     OS.flush();
    172 
    173     // Tell the comment stream that the vector changed underneath it.
    174     DC->CommentsToEmit.clear();
    175     DC->CommentStream.resync();
    176 
    177     assert(OutStringSize != 0 && "Output buffer cannot be zero size");
    178     size_t OutputSize = std::min(OutStringSize-1, InsnStr.size());
    179     std::memcpy(OutString, InsnStr.data(), OutputSize);
    180     OutString[OutputSize] = '\0'; // Terminate string.
    181 
    182     return Size;
    183   }
    184   }
    185   llvm_unreachable("Invalid DecodeStatus!");
    186 }
    187