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//===- BPFDisassembler.cpp - Disassembler for BPF ---------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is part of the BPF Disassembler.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/BPFMCTargetDesc.h"
#include "TargetInfo/BPFTargetInfo.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDisassembler/MCDisassembler.h"
#include "llvm/MC/MCFixedLenDisassembler.h"
#include "llvm/MC/MCInst.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/TargetRegistry.h"
#include <cstdint>
using namespace llvm;
#define DEBUG_TYPE "bpf-disassembler"
typedef MCDisassembler::DecodeStatus DecodeStatus;
namespace {
/// A disassembler class for BPF.
class BPFDisassembler : public MCDisassembler {
public:
enum BPF_CLASS {
BPF_LD = 0x0,
BPF_LDX = 0x1,
BPF_ST = 0x2,
BPF_STX = 0x3,
BPF_ALU = 0x4,
BPF_JMP = 0x5,
BPF_JMP32 = 0x6,
BPF_ALU64 = 0x7
};
enum BPF_SIZE {
BPF_W = 0x0,
BPF_H = 0x1,
BPF_B = 0x2,
BPF_DW = 0x3
};
enum BPF_MODE {
BPF_IMM = 0x0,
BPF_ABS = 0x1,
BPF_IND = 0x2,
BPF_MEM = 0x3,
BPF_LEN = 0x4,
BPF_MSH = 0x5,
BPF_ATOMIC = 0x6
};
BPFDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
: MCDisassembler(STI, Ctx) {}
~BPFDisassembler() override = default;
DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
ArrayRef<uint8_t> Bytes, uint64_t Address,
raw_ostream &CStream) const override;
uint8_t getInstClass(uint64_t Inst) const { return (Inst >> 56) & 0x7; };
uint8_t getInstSize(uint64_t Inst) const { return (Inst >> 59) & 0x3; };
uint8_t getInstMode(uint64_t Inst) const { return (Inst >> 61) & 0x7; };
};
} // end anonymous namespace
static MCDisassembler *createBPFDisassembler(const Target &T,
const MCSubtargetInfo &STI,
MCContext &Ctx) {
return new BPFDisassembler(STI, Ctx);
}
extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFDisassembler() {
// Register the disassembler.
TargetRegistry::RegisterMCDisassembler(getTheBPFTarget(),
createBPFDisassembler);
TargetRegistry::RegisterMCDisassembler(getTheBPFleTarget(),
createBPFDisassembler);
TargetRegistry::RegisterMCDisassembler(getTheBPFbeTarget(),
createBPFDisassembler);
}
static const unsigned GPRDecoderTable[] = {
BPF::R0, BPF::R1, BPF::R2, BPF::R3, BPF::R4, BPF::R5,
BPF::R6, BPF::R7, BPF::R8, BPF::R9, BPF::R10, BPF::R11};
static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo,
uint64_t /*Address*/,
const void * /*Decoder*/) {
if (RegNo > 11)
return MCDisassembler::Fail;
unsigned Reg = GPRDecoderTable[RegNo];
Inst.addOperand(MCOperand::createReg(Reg));
return MCDisassembler::Success;
}
static const unsigned GPR32DecoderTable[] = {
BPF::W0, BPF::W1, BPF::W2, BPF::W3, BPF::W4, BPF::W5,
BPF::W6, BPF::W7, BPF::W8, BPF::W9, BPF::W10, BPF::W11};
static DecodeStatus DecodeGPR32RegisterClass(MCInst &Inst, unsigned RegNo,
uint64_t /*Address*/,
const void * /*Decoder*/) {
if (RegNo > 11)
return MCDisassembler::Fail;
unsigned Reg = GPR32DecoderTable[RegNo];
Inst.addOperand(MCOperand::createReg(Reg));
return MCDisassembler::Success;
}
static DecodeStatus decodeMemoryOpValue(MCInst &Inst, unsigned Insn,
uint64_t Address, const void *Decoder) {
unsigned Register = (Insn >> 16) & 0xf;
if (Register > 11)
return MCDisassembler::Fail;
Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
unsigned Offset = (Insn & 0xffff);
Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset)));
return MCDisassembler::Success;
}
#include "BPFGenDisassemblerTables.inc"
static DecodeStatus readInstruction64(ArrayRef<uint8_t> Bytes, uint64_t Address,
uint64_t &Size, uint64_t &Insn,
bool IsLittleEndian) {
uint64_t Lo, Hi;
if (Bytes.size() < 8) {
Size = 0;
return MCDisassembler::Fail;
}
Size = 8;
if (IsLittleEndian) {
Hi = (Bytes[0] << 24) | (Bytes[1] << 16) | (Bytes[2] << 0) | (Bytes[3] << 8);
Lo = (Bytes[4] << 0) | (Bytes[5] << 8) | (Bytes[6] << 16) | (Bytes[7] << 24);
} else {
Hi = (Bytes[0] << 24) | ((Bytes[1] & 0x0F) << 20) | ((Bytes[1] & 0xF0) << 12) |
(Bytes[2] << 8) | (Bytes[3] << 0);
Lo = (Bytes[4] << 24) | (Bytes[5] << 16) | (Bytes[6] << 8) | (Bytes[7] << 0);
}
Insn = Make_64(Hi, Lo);
return MCDisassembler::Success;
}
DecodeStatus BPFDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
ArrayRef<uint8_t> Bytes,
uint64_t Address,
raw_ostream &CStream) const {
bool IsLittleEndian = getContext().getAsmInfo()->isLittleEndian();
uint64_t Insn, Hi;
DecodeStatus Result;
Result = readInstruction64(Bytes, Address, Size, Insn, IsLittleEndian);
if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
uint8_t InstClass = getInstClass(Insn);
uint8_t InstMode = getInstMode(Insn);
if ((InstClass == BPF_LDX || InstClass == BPF_STX) &&
getInstSize(Insn) != BPF_DW &&
(InstMode == BPF_MEM || InstMode == BPF_ATOMIC) &&
STI.getFeatureBits()[BPF::ALU32])
Result = decodeInstruction(DecoderTableBPFALU3264, Instr, Insn, Address,
this, STI);
else
Result = decodeInstruction(DecoderTableBPF64, Instr, Insn, Address, this,
STI);
if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
switch (Instr.getOpcode()) {
case BPF::LD_imm64:
case BPF::LD_pseudo: {
if (Bytes.size() < 16) {
Size = 0;
return MCDisassembler::Fail;
}
Size = 16;
if (IsLittleEndian)
Hi = (Bytes[12] << 0) | (Bytes[13] << 8) | (Bytes[14] << 16) | (Bytes[15] << 24);
else
Hi = (Bytes[12] << 24) | (Bytes[13] << 16) | (Bytes[14] << 8) | (Bytes[15] << 0);
auto& Op = Instr.getOperand(1);
Op.setImm(Make_64(Hi, Op.getImm()));
break;
}
case BPF::LD_ABS_B:
case BPF::LD_ABS_H:
case BPF::LD_ABS_W:
case BPF::LD_IND_B:
case BPF::LD_IND_H:
case BPF::LD_IND_W: {
auto Op = Instr.getOperand(0);
Instr.clear();
Instr.addOperand(MCOperand::createReg(BPF::R6));
Instr.addOperand(Op);
break;
}
}
return Result;
}
typedef DecodeStatus (*DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address,
const void *Decoder);
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