1 //===-- BPFMCCodeEmitter.cpp - Convert BPF code to machine code -----------===// 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 // This file implements the BPFMCCodeEmitter class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "MCTargetDesc/BPFMCTargetDesc.h" 15 #include "llvm/MC/MCCodeEmitter.h" 16 #include "llvm/MC/MCFixup.h" 17 #include "llvm/MC/MCInst.h" 18 #include "llvm/MC/MCInstrInfo.h" 19 #include "llvm/MC/MCRegisterInfo.h" 20 #include "llvm/MC/MCSubtargetInfo.h" 21 #include "llvm/MC/MCSymbol.h" 22 #include "llvm/ADT/Statistic.h" 23 #include "llvm/Support/raw_ostream.h" 24 using namespace llvm; 25 26 #define DEBUG_TYPE "mccodeemitter" 27 28 namespace { 29 class BPFMCCodeEmitter : public MCCodeEmitter { 30 BPFMCCodeEmitter(const BPFMCCodeEmitter &) = delete; 31 void operator=(const BPFMCCodeEmitter &) = delete; 32 const MCRegisterInfo &MRI; 33 34 public: 35 BPFMCCodeEmitter(const MCRegisterInfo &mri) : MRI(mri) {} 36 37 ~BPFMCCodeEmitter() {} 38 39 // getBinaryCodeForInstr - TableGen'erated function for getting the 40 // binary encoding for an instruction. 41 uint64_t getBinaryCodeForInstr(const MCInst &MI, 42 SmallVectorImpl<MCFixup> &Fixups, 43 const MCSubtargetInfo &STI) const; 44 45 // getMachineOpValue - Return binary encoding of operand. If the machin 46 // operand requires relocation, record the relocation and return zero. 47 unsigned getMachineOpValue(const MCInst &MI, const MCOperand &MO, 48 SmallVectorImpl<MCFixup> &Fixups, 49 const MCSubtargetInfo &STI) const; 50 51 uint64_t getMemoryOpValue(const MCInst &MI, unsigned Op, 52 SmallVectorImpl<MCFixup> &Fixups, 53 const MCSubtargetInfo &STI) const; 54 55 void EncodeInstruction(const MCInst &MI, raw_ostream &OS, 56 SmallVectorImpl<MCFixup> &Fixups, 57 const MCSubtargetInfo &STI) const override; 58 }; 59 } 60 61 MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII, 62 const MCRegisterInfo &MRI, 63 const MCSubtargetInfo &STI, 64 MCContext &Ctx) { 65 return new BPFMCCodeEmitter(MRI); 66 } 67 68 unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI, 69 const MCOperand &MO, 70 SmallVectorImpl<MCFixup> &Fixups, 71 const MCSubtargetInfo &STI) const { 72 if (MO.isReg()) 73 return MRI.getEncodingValue(MO.getReg()); 74 if (MO.isImm()) 75 return static_cast<unsigned>(MO.getImm()); 76 77 assert(MO.isExpr()); 78 79 const MCExpr *Expr = MO.getExpr(); 80 MCExpr::ExprKind Kind = Expr->getKind(); 81 82 assert(Kind == MCExpr::SymbolRef); 83 84 if (MI.getOpcode() == BPF::JAL) 85 // func call name 86 Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_4)); 87 else if (MI.getOpcode() == BPF::LD_imm64) 88 Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_8)); 89 else 90 // bb label 91 Fixups.push_back(MCFixup::Create(0, Expr, FK_PCRel_2)); 92 93 return 0; 94 } 95 96 // Emit one byte through output stream 97 void EmitByte(unsigned char C, unsigned &CurByte, raw_ostream &OS) { 98 OS << (char)C; 99 ++CurByte; 100 } 101 102 // Emit a series of bytes (little endian) 103 void EmitLEConstant(uint64_t Val, unsigned Size, unsigned &CurByte, 104 raw_ostream &OS) { 105 assert(Size <= 8 && "size too big in emit constant"); 106 107 for (unsigned i = 0; i != Size; ++i) { 108 EmitByte(Val & 255, CurByte, OS); 109 Val >>= 8; 110 } 111 } 112 113 // Emit a series of bytes (big endian) 114 void EmitBEConstant(uint64_t Val, unsigned Size, unsigned &CurByte, 115 raw_ostream &OS) { 116 assert(Size <= 8 && "size too big in emit constant"); 117 118 for (int i = (Size - 1) * 8; i >= 0; i -= 8) 119 EmitByte((Val >> i) & 255, CurByte, OS); 120 } 121 122 void BPFMCCodeEmitter::EncodeInstruction(const MCInst &MI, raw_ostream &OS, 123 SmallVectorImpl<MCFixup> &Fixups, 124 const MCSubtargetInfo &STI) const { 125 unsigned Opcode = MI.getOpcode(); 126 // Keep track of the current byte being emitted 127 unsigned CurByte = 0; 128 129 if (Opcode == BPF::LD_imm64) { 130 uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI); 131 EmitByte(Value >> 56, CurByte, OS); 132 EmitByte(((Value >> 48) & 0xff), CurByte, OS); 133 EmitLEConstant(0, 2, CurByte, OS); 134 EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS); 135 136 const MCOperand &MO = MI.getOperand(1); 137 uint64_t Imm = MO.isImm() ? MO.getImm() : 0; 138 EmitByte(0, CurByte, OS); 139 EmitByte(0, CurByte, OS); 140 EmitLEConstant(0, 2, CurByte, OS); 141 EmitLEConstant(Imm >> 32, 4, CurByte, OS); 142 } else { 143 // Get instruction encoding and emit it 144 uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI); 145 EmitByte(Value >> 56, CurByte, OS); 146 EmitByte((Value >> 48) & 0xff, CurByte, OS); 147 EmitLEConstant((Value >> 32) & 0xffff, 2, CurByte, OS); 148 EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS); 149 } 150 } 151 152 // Encode BPF Memory Operand 153 uint64_t BPFMCCodeEmitter::getMemoryOpValue(const MCInst &MI, unsigned Op, 154 SmallVectorImpl<MCFixup> &Fixups, 155 const MCSubtargetInfo &STI) const { 156 uint64_t Encoding; 157 const MCOperand Op1 = MI.getOperand(1); 158 assert(Op1.isReg() && "First operand is not register."); 159 Encoding = MRI.getEncodingValue(Op1.getReg()); 160 Encoding <<= 16; 161 MCOperand Op2 = MI.getOperand(2); 162 assert(Op2.isImm() && "Second operand is not immediate."); 163 Encoding |= Op2.getImm() & 0xffff; 164 return Encoding; 165 } 166 167 #include "BPFGenMCCodeEmitter.inc" 168