1 //===-- lib/MC/MCExternalSymbolizer.cpp - External symbolizer ---*- C++ -*-===// 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 "llvm/MC/MCExternalSymbolizer.h" 11 #include "llvm/MC/MCContext.h" 12 #include "llvm/MC/MCExpr.h" 13 #include "llvm/MC/MCInst.h" 14 #include "llvm/Support/raw_ostream.h" 15 #include <cstring> 16 17 using namespace llvm; 18 19 // This function tries to add a symbolic operand in place of the immediate 20 // Value in the MCInst. The immediate Value has had any PC adjustment made by 21 // the caller. If the instruction is a branch instruction then IsBranch is true, 22 // else false. If the getOpInfo() function was set as part of the 23 // setupForSymbolicDisassembly() call then that function is called to get any 24 // symbolic information at the Address for this instruction. If that returns 25 // non-zero then the symbolic information it returns is used to create an MCExpr 26 // and that is added as an operand to the MCInst. If getOpInfo() returns zero 27 // and IsBranch is true then a symbol look up for Value is done and if a symbol 28 // is found an MCExpr is created with that, else an MCExpr with Value is 29 // created. This function returns true if it adds an operand to the MCInst and 30 // false otherwise. 31 bool MCExternalSymbolizer::tryAddingSymbolicOperand(MCInst &MI, 32 raw_ostream &cStream, 33 int64_t Value, 34 uint64_t Address, 35 bool IsBranch, 36 uint64_t Offset, 37 uint64_t InstSize) { 38 struct LLVMOpInfo1 SymbolicOp; 39 std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1)); 40 SymbolicOp.Value = Value; 41 42 if (!GetOpInfo || 43 !GetOpInfo(DisInfo, Address, Offset, InstSize, 1, &SymbolicOp)) { 44 // Clear SymbolicOp.Value from above and also all other fields. 45 std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1)); 46 if (!SymbolLookUp) 47 return false; 48 uint64_t ReferenceType; 49 if (IsBranch) 50 ReferenceType = LLVMDisassembler_ReferenceType_In_Branch; 51 else 52 ReferenceType = LLVMDisassembler_ReferenceType_InOut_None; 53 const char *ReferenceName; 54 const char *Name = SymbolLookUp(DisInfo, Value, &ReferenceType, Address, 55 &ReferenceName); 56 if (Name) { 57 SymbolicOp.AddSymbol.Name = Name; 58 SymbolicOp.AddSymbol.Present = true; 59 } 60 // For branches always create an MCExpr so it gets printed as hex address. 61 else if (IsBranch) { 62 SymbolicOp.Value = Value; 63 } 64 if(ReferenceType == LLVMDisassembler_ReferenceType_Out_SymbolStub) 65 cStream << "symbol stub for: " << ReferenceName; 66 if (!Name && !IsBranch) 67 return false; 68 } 69 70 const MCExpr *Add = NULL; 71 if (SymbolicOp.AddSymbol.Present) { 72 if (SymbolicOp.AddSymbol.Name) { 73 StringRef Name(SymbolicOp.AddSymbol.Name); 74 MCSymbol *Sym = Ctx.GetOrCreateSymbol(Name); 75 Add = MCSymbolRefExpr::Create(Sym, Ctx); 76 } else { 77 Add = MCConstantExpr::Create((int)SymbolicOp.AddSymbol.Value, Ctx); 78 } 79 } 80 81 const MCExpr *Sub = NULL; 82 if (SymbolicOp.SubtractSymbol.Present) { 83 if (SymbolicOp.SubtractSymbol.Name) { 84 StringRef Name(SymbolicOp.SubtractSymbol.Name); 85 MCSymbol *Sym = Ctx.GetOrCreateSymbol(Name); 86 Sub = MCSymbolRefExpr::Create(Sym, Ctx); 87 } else { 88 Sub = MCConstantExpr::Create((int)SymbolicOp.SubtractSymbol.Value, Ctx); 89 } 90 } 91 92 const MCExpr *Off = NULL; 93 if (SymbolicOp.Value != 0) 94 Off = MCConstantExpr::Create(SymbolicOp.Value, Ctx); 95 96 const MCExpr *Expr; 97 if (Sub) { 98 const MCExpr *LHS; 99 if (Add) 100 LHS = MCBinaryExpr::CreateSub(Add, Sub, Ctx); 101 else 102 LHS = MCUnaryExpr::CreateMinus(Sub, Ctx); 103 if (Off != 0) 104 Expr = MCBinaryExpr::CreateAdd(LHS, Off, Ctx); 105 else 106 Expr = LHS; 107 } else if (Add) { 108 if (Off != 0) 109 Expr = MCBinaryExpr::CreateAdd(Add, Off, Ctx); 110 else 111 Expr = Add; 112 } else { 113 if (Off != 0) 114 Expr = Off; 115 else 116 Expr = MCConstantExpr::Create(0, Ctx); 117 } 118 119 Expr = RelInfo->createExprForCAPIVariantKind(Expr, SymbolicOp.VariantKind); 120 if (!Expr) 121 return false; 122 123 MI.addOperand(MCOperand::CreateExpr(Expr)); 124 return true; 125 } 126 127 // This function tries to add a comment as to what is being referenced by a load 128 // instruction with the base register that is the Pc. These can often be values 129 // in a literal pool near the Address of the instruction. The Address of the 130 // instruction and its immediate Value are used as a possible literal pool entry. 131 // The SymbolLookUp call back will return the name of a symbol referenced by the 132 // literal pool's entry if the referenced address is that of a symbol. Or it 133 // will return a pointer to a literal 'C' string if the referenced address of 134 // the literal pool's entry is an address into a section with C string literals. 135 void MCExternalSymbolizer::tryAddingPcLoadReferenceComment(raw_ostream &cStream, 136 int64_t Value, 137 uint64_t Address) { 138 if (SymbolLookUp) { 139 uint64_t ReferenceType = LLVMDisassembler_ReferenceType_In_PCrel_Load; 140 const char *ReferenceName; 141 (void)SymbolLookUp(DisInfo, Value, &ReferenceType, Address, &ReferenceName); 142 if(ReferenceType == LLVMDisassembler_ReferenceType_Out_LitPool_SymAddr || 143 ReferenceType == LLVMDisassembler_ReferenceType_Out_LitPool_CstrAddr) 144 cStream << "literal pool for: " << ReferenceName; 145 } 146 } 147 148 namespace llvm { 149 MCSymbolizer *createMCSymbolizer(StringRef TT, LLVMOpInfoCallback GetOpInfo, 150 LLVMSymbolLookupCallback SymbolLookUp, 151 void *DisInfo, 152 MCContext *Ctx, 153 MCRelocationInfo *RelInfo) { 154 assert(Ctx != 0 && "No MCContext given for symbolic disassembly"); 155 156 OwningPtr<MCRelocationInfo> RelInfoOwingPtr(RelInfo); 157 return new MCExternalSymbolizer(*Ctx, RelInfoOwingPtr, GetOpInfo, 158 SymbolLookUp, DisInfo); 159 } 160 } 161