1 //===-- BPFMCCodeEmitter.cpp - Convert BPF code to machine code -----------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements the BPFMCCodeEmitter class. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "MCTargetDesc/BPFMCTargetDesc.h" 14 #include "llvm/ADT/SmallVector.h" 15 #include "llvm/MC/MCCodeEmitter.h" 16 #include "llvm/MC/MCExpr.h" 17 #include "llvm/MC/MCFixup.h" 18 #include "llvm/MC/MCInst.h" 19 #include "llvm/MC/MCInstrInfo.h" 20 #include "llvm/MC/MCRegisterInfo.h" 21 #include "llvm/MC/MCSubtargetInfo.h" 22 #include "llvm/Support/Endian.h" 23 #include "llvm/Support/EndianStream.h" 24 #include <cassert> 25 #include <cstdint> 26 27 using namespace llvm; 28 29 #define DEBUG_TYPE "mccodeemitter" 30 31 namespace { 32 33 class BPFMCCodeEmitter : public MCCodeEmitter { 34 const MCRegisterInfo &MRI; 35 bool IsLittleEndian; 36 37 public: 38 BPFMCCodeEmitter(const MCInstrInfo &, const MCRegisterInfo &mri, 39 bool IsLittleEndian) 40 : MRI(mri), IsLittleEndian(IsLittleEndian) { } 41 BPFMCCodeEmitter(const BPFMCCodeEmitter &) = delete; 42 void operator=(const BPFMCCodeEmitter &) = delete; 43 ~BPFMCCodeEmitter() override = default; 44 45 // getBinaryCodeForInstr - TableGen'erated function for getting the 46 // binary encoding for an instruction. 47 uint64_t getBinaryCodeForInstr(const MCInst &MI, 48 SmallVectorImpl<MCFixup> &Fixups, 49 const MCSubtargetInfo &STI) const; 50 51 // getMachineOpValue - Return binary encoding of operand. If the machin 52 // operand requires relocation, record the relocation and return zero. 53 unsigned getMachineOpValue(const MCInst &MI, const MCOperand &MO, 54 SmallVectorImpl<MCFixup> &Fixups, 55 const MCSubtargetInfo &STI) const; 56 57 uint64_t getMemoryOpValue(const MCInst &MI, unsigned Op, 58 SmallVectorImpl<MCFixup> &Fixups, 59 const MCSubtargetInfo &STI) const; 60 61 void encodeInstruction(const MCInst &MI, SmallVectorImpl<char> &CB, 62 SmallVectorImpl<MCFixup> &Fixups, 63 const MCSubtargetInfo &STI) const override; 64 }; 65 66 } // end anonymous namespace 67 68 MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII, 69 MCContext &Ctx) { 70 return new BPFMCCodeEmitter(MCII, *Ctx.getRegisterInfo(), true); 71 } 72 73 MCCodeEmitter *llvm::createBPFbeMCCodeEmitter(const MCInstrInfo &MCII, 74 MCContext &Ctx) { 75 return new BPFMCCodeEmitter(MCII, *Ctx.getRegisterInfo(), false); 76 } 77 78 unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI, 79 const MCOperand &MO, 80 SmallVectorImpl<MCFixup> &Fixups, 81 const MCSubtargetInfo &STI) const { 82 if (MO.isReg()) 83 return MRI.getEncodingValue(MO.getReg()); 84 if (MO.isImm()) 85 return static_cast<unsigned>(MO.getImm()); 86 87 assert(MO.isExpr()); 88 89 const MCExpr *Expr = MO.getExpr(); 90 91 assert(Expr->getKind() == MCExpr::SymbolRef); 92 93 if (MI.getOpcode() == BPF::JAL) 94 // func call name 95 Fixups.push_back(MCFixup::create(0, Expr, FK_PCRel_4)); 96 else if (MI.getOpcode() == BPF::LD_imm64) 97 Fixups.push_back(MCFixup::create(0, Expr, FK_SecRel_8)); 98 else 99 // bb label 100 Fixups.push_back(MCFixup::create(0, Expr, FK_PCRel_2)); 101 102 return 0; 103 } 104 105 static uint8_t SwapBits(uint8_t Val) 106 { 107 return (Val & 0x0F) << 4 | (Val & 0xF0) >> 4; 108 } 109 110 void BPFMCCodeEmitter::encodeInstruction(const MCInst &MI, 111 SmallVectorImpl<char> &CB, 112 SmallVectorImpl<MCFixup> &Fixups, 113 const MCSubtargetInfo &STI) const { 114 unsigned Opcode = MI.getOpcode(); 115 raw_svector_ostream OS(CB); 116 support::endian::Writer OSE(OS, 117 IsLittleEndian ? support::little : support::big); 118 119 if (Opcode == BPF::LD_imm64 || Opcode == BPF::LD_pseudo) { 120 uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI); 121 CB.push_back(Value >> 56); 122 if (IsLittleEndian) 123 CB.push_back((Value >> 48) & 0xff); 124 else 125 CB.push_back(SwapBits((Value >> 48) & 0xff)); 126 OSE.write<uint16_t>(0); 127 OSE.write<uint32_t>(Value & 0xffffFFFF); 128 129 const MCOperand &MO = MI.getOperand(1); 130 uint64_t Imm = MO.isImm() ? MO.getImm() : 0; 131 OSE.write<uint8_t>(0); 132 OSE.write<uint8_t>(0); 133 OSE.write<uint16_t>(0); 134 OSE.write<uint32_t>(Imm >> 32); 135 } else { 136 // Get instruction encoding and emit it 137 uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI); 138 CB.push_back(Value >> 56); 139 if (IsLittleEndian) 140 CB.push_back(char((Value >> 48) & 0xff)); 141 else 142 CB.push_back(SwapBits((Value >> 48) & 0xff)); 143 OSE.write<uint16_t>((Value >> 32) & 0xffff); 144 OSE.write<uint32_t>(Value & 0xffffFFFF); 145 } 146 } 147 148 // Encode BPF Memory Operand 149 uint64_t BPFMCCodeEmitter::getMemoryOpValue(const MCInst &MI, unsigned Op, 150 SmallVectorImpl<MCFixup> &Fixups, 151 const MCSubtargetInfo &STI) const { 152 // For CMPXCHG instructions, output is implicitly in R0/W0, 153 // so memory operand starts from operand 0. 154 int MemOpStartIndex = 1, Opcode = MI.getOpcode(); 155 if (Opcode == BPF::CMPXCHGW32 || Opcode == BPF::CMPXCHGD) 156 MemOpStartIndex = 0; 157 158 uint64_t Encoding; 159 const MCOperand Op1 = MI.getOperand(MemOpStartIndex); 160 assert(Op1.isReg() && "First operand is not register."); 161 Encoding = MRI.getEncodingValue(Op1.getReg()); 162 Encoding <<= 16; 163 MCOperand Op2 = MI.getOperand(MemOpStartIndex + 1); 164 assert(Op2.isImm() && "Second operand is not immediate."); 165 Encoding |= Op2.getImm() & 0xffff; 166 return Encoding; 167 } 168 169 #include "BPFGenMCCodeEmitter.inc" 170