1 //===- BPFDisassembler.cpp - Disassembler for BPF ---------------*- 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 // This file is part of the BPF Disassembler. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "BPF.h" 15 #include "BPFSubtarget.h" 16 #include "MCTargetDesc/BPFMCTargetDesc.h" 17 #include "llvm/ADT/ArrayRef.h" 18 #include "llvm/MC/MCAsmInfo.h" 19 #include "llvm/MC/MCContext.h" 20 #include "llvm/MC/MCDisassembler/MCDisassembler.h" 21 #include "llvm/MC/MCFixedLenDisassembler.h" 22 #include "llvm/MC/MCInst.h" 23 #include "llvm/Support/MathExtras.h" 24 #include "llvm/Support/TargetRegistry.h" 25 #include <cstdint> 26 27 using namespace llvm; 28 29 #define DEBUG_TYPE "bpf-disassembler" 30 31 typedef MCDisassembler::DecodeStatus DecodeStatus; 32 33 namespace { 34 35 /// A disassembler class for BPF. 36 class BPFDisassembler : public MCDisassembler { 37 public: 38 BPFDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx) 39 : MCDisassembler(STI, Ctx) {} 40 ~BPFDisassembler() override = default; 41 42 DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size, 43 ArrayRef<uint8_t> Bytes, uint64_t Address, 44 raw_ostream &VStream, 45 raw_ostream &CStream) const override; 46 }; 47 48 } // end anonymous namespace 49 50 static MCDisassembler *createBPFDisassembler(const Target &T, 51 const MCSubtargetInfo &STI, 52 MCContext &Ctx) { 53 return new BPFDisassembler(STI, Ctx); 54 } 55 56 57 extern "C" void LLVMInitializeBPFDisassembler() { 58 // Register the disassembler. 59 TargetRegistry::RegisterMCDisassembler(getTheBPFTarget(), 60 createBPFDisassembler); 61 TargetRegistry::RegisterMCDisassembler(getTheBPFleTarget(), 62 createBPFDisassembler); 63 TargetRegistry::RegisterMCDisassembler(getTheBPFbeTarget(), 64 createBPFDisassembler); 65 } 66 67 static const unsigned GPRDecoderTable[] = { 68 BPF::R0, BPF::R1, BPF::R2, BPF::R3, BPF::R4, BPF::R5, 69 BPF::R6, BPF::R7, BPF::R8, BPF::R9, BPF::R10, BPF::R11}; 70 71 static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo, 72 uint64_t /*Address*/, 73 const void * /*Decoder*/) { 74 if (RegNo > 11) 75 return MCDisassembler::Fail; 76 77 unsigned Reg = GPRDecoderTable[RegNo]; 78 Inst.addOperand(MCOperand::createReg(Reg)); 79 return MCDisassembler::Success; 80 } 81 82 static DecodeStatus decodeMemoryOpValue(MCInst &Inst, unsigned Insn, 83 uint64_t Address, const void *Decoder) { 84 unsigned Register = (Insn >> 16) & 0xf; 85 Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register])); 86 unsigned Offset = (Insn & 0xffff); 87 Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset))); 88 89 return MCDisassembler::Success; 90 } 91 92 #include "BPFGenDisassemblerTables.inc" 93 static DecodeStatus readInstruction64(ArrayRef<uint8_t> Bytes, uint64_t Address, 94 uint64_t &Size, uint64_t &Insn, 95 bool IsLittleEndian) { 96 uint64_t Lo, Hi; 97 98 if (Bytes.size() < 8) { 99 Size = 0; 100 return MCDisassembler::Fail; 101 } 102 103 Size = 8; 104 if (IsLittleEndian) { 105 Hi = (Bytes[0] << 24) | (Bytes[1] << 16) | (Bytes[2] << 0) | (Bytes[3] << 8); 106 Lo = (Bytes[4] << 0) | (Bytes[5] << 8) | (Bytes[6] << 16) | (Bytes[7] << 24); 107 } else { 108 Hi = (Bytes[0] << 24) | ((Bytes[1] & 0x0F) << 20) | ((Bytes[1] & 0xF0) << 12) | 109 (Bytes[2] << 8) | (Bytes[3] << 0); 110 Lo = (Bytes[4] << 24) | (Bytes[5] << 16) | (Bytes[6] << 8) | (Bytes[7] << 0); 111 } 112 Insn = Make_64(Hi, Lo); 113 114 return MCDisassembler::Success; 115 } 116 117 DecodeStatus BPFDisassembler::getInstruction(MCInst &Instr, uint64_t &Size, 118 ArrayRef<uint8_t> Bytes, 119 uint64_t Address, 120 raw_ostream &VStream, 121 raw_ostream &CStream) const { 122 bool IsLittleEndian = getContext().getAsmInfo()->isLittleEndian(); 123 uint64_t Insn, Hi; 124 DecodeStatus Result; 125 126 Result = readInstruction64(Bytes, Address, Size, Insn, IsLittleEndian); 127 if (Result == MCDisassembler::Fail) return MCDisassembler::Fail; 128 129 Result = decodeInstruction(DecoderTableBPF64, Instr, Insn, 130 Address, this, STI); 131 if (Result == MCDisassembler::Fail) return MCDisassembler::Fail; 132 133 switch (Instr.getOpcode()) { 134 case BPF::LD_imm64: { 135 if (Bytes.size() < 16) { 136 Size = 0; 137 return MCDisassembler::Fail; 138 } 139 Size = 16; 140 if (IsLittleEndian) 141 Hi = (Bytes[12] << 0) | (Bytes[13] << 8) | (Bytes[14] << 16) | (Bytes[15] << 24); 142 else 143 Hi = (Bytes[12] << 24) | (Bytes[13] << 16) | (Bytes[14] << 8) | (Bytes[15] << 0); 144 auto& Op = Instr.getOperand(1); 145 Op.setImm(Make_64(Hi, Op.getImm())); 146 break; 147 } 148 case BPF::LD_ABS_B: 149 case BPF::LD_ABS_H: 150 case BPF::LD_ABS_W: 151 case BPF::LD_IND_B: 152 case BPF::LD_IND_H: 153 case BPF::LD_IND_W: { 154 auto Op = Instr.getOperand(0); 155 Instr.clear(); 156 Instr.addOperand(MCOperand::createReg(BPF::R6)); 157 Instr.addOperand(Op); 158 break; 159 } 160 } 161 162 return Result; 163 } 164 165 typedef DecodeStatus (*DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address, 166 const void *Decoder); 167