1 //===- BPFDisassembler.cpp - Disassembler for BPF ---------------*- C++ -*-===// 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 is part of the BPF Disassembler. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "MCTargetDesc/BPFMCTargetDesc.h" 14 #include "TargetInfo/BPFTargetInfo.h" 15 #include "llvm/ADT/ArrayRef.h" 16 #include "llvm/MC/MCAsmInfo.h" 17 #include "llvm/MC/MCContext.h" 18 #include "llvm/MC/MCDisassembler/MCDisassembler.h" 19 #include "llvm/MC/MCFixedLenDisassembler.h" 20 #include "llvm/MC/MCInst.h" 21 #include "llvm/MC/SubtargetFeature.h" 22 #include "llvm/MC/TargetRegistry.h" 23 #include "llvm/Support/MathExtras.h" 24 #include <cstdint> 25 26 using namespace llvm; 27 28 #define DEBUG_TYPE "bpf-disassembler" 29 30 typedef MCDisassembler::DecodeStatus DecodeStatus; 31 32 namespace { 33 34 /// A disassembler class for BPF. 35 class BPFDisassembler : public MCDisassembler { 36 public: 37 enum BPF_CLASS { 38 BPF_LD = 0x0, 39 BPF_LDX = 0x1, 40 BPF_ST = 0x2, 41 BPF_STX = 0x3, 42 BPF_ALU = 0x4, 43 BPF_JMP = 0x5, 44 BPF_JMP32 = 0x6, 45 BPF_ALU64 = 0x7 46 }; 47 48 enum BPF_SIZE { 49 BPF_W = 0x0, 50 BPF_H = 0x1, 51 BPF_B = 0x2, 52 BPF_DW = 0x3 53 }; 54 55 enum BPF_MODE { 56 BPF_IMM = 0x0, 57 BPF_ABS = 0x1, 58 BPF_IND = 0x2, 59 BPF_MEM = 0x3, 60 BPF_LEN = 0x4, 61 BPF_MSH = 0x5, 62 BPF_ATOMIC = 0x6 63 }; 64 65 BPFDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx) 66 : MCDisassembler(STI, Ctx) {} 67 ~BPFDisassembler() override = default; 68 69 DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size, 70 ArrayRef<uint8_t> Bytes, uint64_t Address, 71 raw_ostream &CStream) const override; 72 73 uint8_t getInstClass(uint64_t Inst) const { return (Inst >> 56) & 0x7; }; 74 uint8_t getInstSize(uint64_t Inst) const { return (Inst >> 59) & 0x3; }; 75 uint8_t getInstMode(uint64_t Inst) const { return (Inst >> 61) & 0x7; }; 76 }; 77 78 } // end anonymous namespace 79 80 static MCDisassembler *createBPFDisassembler(const Target &T, 81 const MCSubtargetInfo &STI, 82 MCContext &Ctx) { 83 return new BPFDisassembler(STI, Ctx); 84 } 85 86 87 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFDisassembler() { 88 // Register the disassembler. 89 TargetRegistry::RegisterMCDisassembler(getTheBPFTarget(), 90 createBPFDisassembler); 91 TargetRegistry::RegisterMCDisassembler(getTheBPFleTarget(), 92 createBPFDisassembler); 93 TargetRegistry::RegisterMCDisassembler(getTheBPFbeTarget(), 94 createBPFDisassembler); 95 } 96 97 static const unsigned GPRDecoderTable[] = { 98 BPF::R0, BPF::R1, BPF::R2, BPF::R3, BPF::R4, BPF::R5, 99 BPF::R6, BPF::R7, BPF::R8, BPF::R9, BPF::R10, BPF::R11}; 100 101 static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo, 102 uint64_t /*Address*/, 103 const void * /*Decoder*/) { 104 if (RegNo > 11) 105 return MCDisassembler::Fail; 106 107 unsigned Reg = GPRDecoderTable[RegNo]; 108 Inst.addOperand(MCOperand::createReg(Reg)); 109 return MCDisassembler::Success; 110 } 111 112 static const unsigned GPR32DecoderTable[] = { 113 BPF::W0, BPF::W1, BPF::W2, BPF::W3, BPF::W4, BPF::W5, 114 BPF::W6, BPF::W7, BPF::W8, BPF::W9, BPF::W10, BPF::W11}; 115 116 static DecodeStatus DecodeGPR32RegisterClass(MCInst &Inst, unsigned RegNo, 117 uint64_t /*Address*/, 118 const void * /*Decoder*/) { 119 if (RegNo > 11) 120 return MCDisassembler::Fail; 121 122 unsigned Reg = GPR32DecoderTable[RegNo]; 123 Inst.addOperand(MCOperand::createReg(Reg)); 124 return MCDisassembler::Success; 125 } 126 127 static DecodeStatus decodeMemoryOpValue(MCInst &Inst, unsigned Insn, 128 uint64_t Address, const void *Decoder) { 129 unsigned Register = (Insn >> 16) & 0xf; 130 if (Register > 11) 131 return MCDisassembler::Fail; 132 133 Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register])); 134 unsigned Offset = (Insn & 0xffff); 135 Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset))); 136 137 return MCDisassembler::Success; 138 } 139 140 #include "BPFGenDisassemblerTables.inc" 141 static DecodeStatus readInstruction64(ArrayRef<uint8_t> Bytes, uint64_t Address, 142 uint64_t &Size, uint64_t &Insn, 143 bool IsLittleEndian) { 144 uint64_t Lo, Hi; 145 146 if (Bytes.size() < 8) { 147 Size = 0; 148 return MCDisassembler::Fail; 149 } 150 151 Size = 8; 152 if (IsLittleEndian) { 153 Hi = (Bytes[0] << 24) | (Bytes[1] << 16) | (Bytes[2] << 0) | (Bytes[3] << 8); 154 Lo = (Bytes[4] << 0) | (Bytes[5] << 8) | (Bytes[6] << 16) | (Bytes[7] << 24); 155 } else { 156 Hi = (Bytes[0] << 24) | ((Bytes[1] & 0x0F) << 20) | ((Bytes[1] & 0xF0) << 12) | 157 (Bytes[2] << 8) | (Bytes[3] << 0); 158 Lo = (Bytes[4] << 24) | (Bytes[5] << 16) | (Bytes[6] << 8) | (Bytes[7] << 0); 159 } 160 Insn = Make_64(Hi, Lo); 161 162 return MCDisassembler::Success; 163 } 164 165 DecodeStatus BPFDisassembler::getInstruction(MCInst &Instr, uint64_t &Size, 166 ArrayRef<uint8_t> Bytes, 167 uint64_t Address, 168 raw_ostream &CStream) const { 169 bool IsLittleEndian = getContext().getAsmInfo()->isLittleEndian(); 170 uint64_t Insn, Hi; 171 DecodeStatus Result; 172 173 Result = readInstruction64(Bytes, Address, Size, Insn, IsLittleEndian); 174 if (Result == MCDisassembler::Fail) return MCDisassembler::Fail; 175 176 uint8_t InstClass = getInstClass(Insn); 177 uint8_t InstMode = getInstMode(Insn); 178 if ((InstClass == BPF_LDX || InstClass == BPF_STX) && 179 getInstSize(Insn) != BPF_DW && 180 (InstMode == BPF_MEM || InstMode == BPF_ATOMIC) && 181 STI.getFeatureBits()[BPF::ALU32]) 182 Result = decodeInstruction(DecoderTableBPFALU3264, Instr, Insn, Address, 183 this, STI); 184 else 185 Result = decodeInstruction(DecoderTableBPF64, Instr, Insn, Address, this, 186 STI); 187 188 if (Result == MCDisassembler::Fail) return MCDisassembler::Fail; 189 190 switch (Instr.getOpcode()) { 191 case BPF::LD_imm64: 192 case BPF::LD_pseudo: { 193 if (Bytes.size() < 16) { 194 Size = 0; 195 return MCDisassembler::Fail; 196 } 197 Size = 16; 198 if (IsLittleEndian) 199 Hi = (Bytes[12] << 0) | (Bytes[13] << 8) | (Bytes[14] << 16) | (Bytes[15] << 24); 200 else 201 Hi = (Bytes[12] << 24) | (Bytes[13] << 16) | (Bytes[14] << 8) | (Bytes[15] << 0); 202 auto& Op = Instr.getOperand(1); 203 Op.setImm(Make_64(Hi, Op.getImm())); 204 break; 205 } 206 case BPF::LD_ABS_B: 207 case BPF::LD_ABS_H: 208 case BPF::LD_ABS_W: 209 case BPF::LD_IND_B: 210 case BPF::LD_IND_H: 211 case BPF::LD_IND_W: { 212 auto Op = Instr.getOperand(0); 213 Instr.clear(); 214 Instr.addOperand(MCOperand::createReg(BPF::R6)); 215 Instr.addOperand(Op); 216 break; 217 } 218 } 219 220 return Result; 221 } 222 223 typedef DecodeStatus (*DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address, 224 const void *Decoder); 225