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