216 lines · cpp
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-exception6//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/MCDecoder.h"19#include "llvm/MC/MCDecoderOps.h"20#include "llvm/MC/MCDisassembler/MCDisassembler.h"21#include "llvm/MC/MCInst.h"22#include "llvm/MC/TargetRegistry.h"23#include "llvm/Support/Compiler.h"24#include "llvm/Support/MathExtras.h"25#include "llvm/TargetParser/SubtargetFeature.h"26#include <cstdint>27 28using namespace llvm;29using namespace llvm::MCD;30 31#define DEBUG_TYPE "bpf-disassembler"32 33typedef MCDisassembler::DecodeStatus DecodeStatus;34 35namespace {36 37/// A disassembler class for BPF.38class BPFDisassembler : public MCDisassembler {39public:40 enum BPF_CLASS {41 BPF_LD = 0x0,42 BPF_LDX = 0x1,43 BPF_ST = 0x2,44 BPF_STX = 0x3,45 BPF_ALU = 0x4,46 BPF_JMP = 0x5,47 BPF_JMP32 = 0x6,48 BPF_ALU64 = 0x749 };50 51 enum BPF_SIZE {52 BPF_W = 0x0,53 BPF_H = 0x1,54 BPF_B = 0x2,55 BPF_DW = 0x356 };57 58 enum BPF_MODE {59 BPF_IMM = 0x0,60 BPF_ABS = 0x1,61 BPF_IND = 0x2,62 BPF_MEM = 0x3,63 BPF_MEMSX = 0x4,64 BPF_ATOMIC = 0x665 };66 67 BPFDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)68 : MCDisassembler(STI, Ctx) {}69 ~BPFDisassembler() override = default;70 71 DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,72 ArrayRef<uint8_t> Bytes, uint64_t Address,73 raw_ostream &CStream) const override;74 75 uint8_t getInstClass(uint64_t Inst) const { return (Inst >> 56) & 0x7; };76 uint8_t getInstSize(uint64_t Inst) const { return (Inst >> 59) & 0x3; };77 uint8_t getInstMode(uint64_t Inst) const { return (Inst >> 61) & 0x7; };78};79 80} // end anonymous namespace81 82static MCDisassembler *createBPFDisassembler(const Target &T,83 const MCSubtargetInfo &STI,84 MCContext &Ctx) {85 return new BPFDisassembler(STI, Ctx);86}87 88extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void89LLVMInitializeBPFDisassembler() {90 // Register the disassembler.91 TargetRegistry::RegisterMCDisassembler(getTheBPFTarget(),92 createBPFDisassembler);93 TargetRegistry::RegisterMCDisassembler(getTheBPFleTarget(),94 createBPFDisassembler);95 TargetRegistry::RegisterMCDisassembler(getTheBPFbeTarget(),96 createBPFDisassembler);97}98 99static const unsigned GPRDecoderTable[] = {100 BPF::R0, BPF::R1, BPF::R2, BPF::R3, BPF::R4, BPF::R5,101 BPF::R6, BPF::R7, BPF::R8, BPF::R9, BPF::R10, BPF::R11};102 103static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo,104 uint64_t /*Address*/,105 const MCDisassembler * /*Decoder*/) {106 if (RegNo > 11)107 return MCDisassembler::Fail;108 109 unsigned Reg = GPRDecoderTable[RegNo];110 Inst.addOperand(MCOperand::createReg(Reg));111 return MCDisassembler::Success;112}113 114static const unsigned GPR32DecoderTable[] = {115 BPF::W0, BPF::W1, BPF::W2, BPF::W3, BPF::W4, BPF::W5,116 BPF::W6, BPF::W7, BPF::W8, BPF::W9, BPF::W10, BPF::W11};117 118static DecodeStatus119DecodeGPR32RegisterClass(MCInst &Inst, unsigned RegNo, uint64_t /*Address*/,120 const MCDisassembler * /*Decoder*/) {121 if (RegNo > 11)122 return MCDisassembler::Fail;123 124 unsigned Reg = GPR32DecoderTable[RegNo];125 Inst.addOperand(MCOperand::createReg(Reg));126 return MCDisassembler::Success;127}128 129static DecodeStatus decodeMemoryOpValue(MCInst &Inst, unsigned Insn,130 uint64_t Address,131 const MCDisassembler *Decoder) {132 unsigned Register = (Insn >> 16) & 0xf;133 if (Register > 11)134 return MCDisassembler::Fail;135 136 Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));137 unsigned Offset = (Insn & 0xffff);138 Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset)));139 140 return MCDisassembler::Success;141}142 143#include "BPFGenDisassemblerTables.inc"144static DecodeStatus readInstruction64(ArrayRef<uint8_t> Bytes, uint64_t Address,145 uint64_t &Size, uint64_t &Insn,146 bool IsLittleEndian) {147 uint64_t Lo, Hi;148 149 if (Bytes.size() < 8) {150 Size = 0;151 return MCDisassembler::Fail;152 }153 154 Size = 8;155 if (IsLittleEndian) {156 Hi = (Bytes[0] << 24) | (Bytes[1] << 16) | (Bytes[2] << 0) | (Bytes[3] << 8);157 Lo = (Bytes[4] << 0) | (Bytes[5] << 8) | (Bytes[6] << 16) | (Bytes[7] << 24);158 } else {159 Hi = (Bytes[0] << 24) | ((Bytes[1] & 0x0F) << 20) | ((Bytes[1] & 0xF0) << 12) |160 (Bytes[2] << 8) | (Bytes[3] << 0);161 Lo = (Bytes[4] << 24) | (Bytes[5] << 16) | (Bytes[6] << 8) | (Bytes[7] << 0);162 }163 Insn = Make_64(Hi, Lo);164 165 return MCDisassembler::Success;166}167 168DecodeStatus BPFDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,169 ArrayRef<uint8_t> Bytes,170 uint64_t Address,171 raw_ostream &CStream) const {172 bool IsLittleEndian = getContext().getAsmInfo()->isLittleEndian();173 uint64_t Insn, Hi;174 DecodeStatus Result;175 176 Result = readInstruction64(Bytes, Address, Size, Insn, IsLittleEndian);177 if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;178 179 uint8_t InstClass = getInstClass(Insn);180 uint8_t InstMode = getInstMode(Insn);181 if ((InstClass == BPF_LDX || InstClass == BPF_STX) &&182 getInstSize(Insn) != BPF_DW &&183 (InstMode == BPF_MEM || InstMode == BPF_ATOMIC) &&184 STI.hasFeature(BPF::ALU32))185 Result = decodeInstruction(DecoderTableBPFALU3264, Instr, Insn, Address,186 this, STI);187 else188 Result = decodeInstruction(DecoderTableBPF64, Instr, Insn, Address, this,189 STI);190 191 if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;192 193 switch (Instr.getOpcode()) {194 case BPF::LD_imm64:195 case BPF::LD_pseudo: {196 if (Bytes.size() < 16) {197 Size = 0;198 return MCDisassembler::Fail;199 }200 Size = 16;201 if (IsLittleEndian)202 Hi = (Bytes[12] << 0) | (Bytes[13] << 8) | (Bytes[14] << 16) | (Bytes[15] << 24);203 else204 Hi = (Bytes[12] << 24) | (Bytes[13] << 16) | (Bytes[14] << 8) | (Bytes[15] << 0);205 auto& Op = Instr.getOperand(1);206 Op.setImm(Make_64(Hi, Op.getImm()));207 break;208 }209 }210 211 return Result;212}213 214typedef DecodeStatus (*DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address,215 const MCDisassembler *Decoder);216