LLVM  9.0.0svn
BPFDisassembler.cpp
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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 
14 #include "llvm/ADT/ArrayRef.h"
15 #include "llvm/MC/MCAsmInfo.h"
16 #include "llvm/MC/MCContext.h"
19 #include "llvm/MC/MCInst.h"
22 #include <cstdint>
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "bpf-disassembler"
27 
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 
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.
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));
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));
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 
134 }
135 
136 #include "BPFGenDisassemblerTables.inc"
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 
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  if ((InstClass == BPF_LDX || InstClass == BPF_STX) &&
175  getInstSize(Insn) != BPF_DW &&
176  getInstMode(Insn) == BPF_MEM &&
177  STI.getFeatureBits()[BPF::ALU32])
178  Result = decodeInstruction(DecoderTableBPFALU3264, Instr, Insn, Address,
179  this, STI);
180  else
181  Result = decodeInstruction(DecoderTableBPF64, Instr, Insn, Address, this,
182  STI);
183 
184  if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
185 
186  switch (Instr.getOpcode()) {
187  case BPF::LD_imm64:
188  case BPF::LD_pseudo: {
189  if (Bytes.size() < 16) {
190  Size = 0;
191  return MCDisassembler::Fail;
192  }
193  Size = 16;
194  if (IsLittleEndian)
195  Hi = (Bytes[12] << 0) | (Bytes[13] << 8) | (Bytes[14] << 16) | (Bytes[15] << 24);
196  else
197  Hi = (Bytes[12] << 24) | (Bytes[13] << 16) | (Bytes[14] << 8) | (Bytes[15] << 0);
198  auto& Op = Instr.getOperand(1);
199  Op.setImm(Make_64(Hi, Op.getImm()));
200  break;
201  }
202  case BPF::LD_ABS_B:
203  case BPF::LD_ABS_H:
204  case BPF::LD_ABS_W:
205  case BPF::LD_IND_B:
206  case BPF::LD_IND_H:
207  case BPF::LD_IND_W: {
208  auto Op = Instr.getOperand(0);
209  Instr.clear();
211  Instr.addOperand(Op);
212  break;
213  }
214  }
215 
216  return Result;
217 }
218 
219 typedef DecodeStatus (*DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address,
220  const void *Decoder);
#define R4(n)
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void clear()
Definition: MCInst.h:188
DecodeStatus(* DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address, const void *Decoder)
DecodeStatus
Ternary decode status.
Superclass for all disassemblers.
unsigned Reg
static void RegisterMCDisassembler(Target &T, Target::MCDisassemblerCtorTy Fn)
RegisterMCDisassembler - Register a MCDisassembler implementation for the given target.
#define R2(n)
static DecodeStatus readInstruction64(ArrayRef< uint8_t > Bytes, uint64_t Address, uint64_t &Size, uint64_t &Insn, bool IsLittleEndian)
static MCOperand createReg(unsigned Reg)
Definition: MCInst.h:115
Context object for machine code objects.
Definition: MCContext.h:62
static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo, uint64_t, const void *)
int decodeInstruction(InternalInstruction *insn, byteReader_t reader, const void *readerArg, dlog_t logger, void *loggerArg, const void *miiArg, uint64_t startLoc, DisassemblerMode mode)
Decode one instruction and store the decoding results in a buffer provided by the consumer...
static const unsigned GPRDecoderTable[]
Instances of this class represent a single low-level machine instruction.
Definition: MCInst.h:158
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:148
#define R6(n)
static MCDisassembler * createBPFDisassembler(const Target &T, const MCSubtargetInfo &STI, MCContext &Ctx)
const MCOperand & getOperand(unsigned i) const
Definition: MCInst.h:179
Promote Memory to Register
Definition: Mem2Reg.cpp:109
void LLVMInitializeBPFDisassembler()
Target - Wrapper for Target specific information.
static DecodeStatus decodeMemoryOpValue(MCInst &Inst, unsigned Insn, uint64_t Address, const void *Decoder)
Generic base class for all target subtargets.
uint32_t Size
Definition: Profile.cpp:46
Target & getTheBPFleTarget()
static DecodeStatus DecodeGPR32RegisterClass(MCInst &Inst, unsigned RegNo, uint64_t, const void *)
constexpr uint64_t Make_64(uint32_t High, uint32_t Low)
Make a 64-bit integer from a high / low pair of 32-bit integers.
Definition: MathExtras.h:293
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45
IRTranslator LLVM IR MI
void addOperand(const MCOperand &Op)
Definition: MCInst.h:183
static const unsigned GPR32DecoderTable[]
Target & getTheBPFbeTarget()
unsigned getOpcode() const
Definition: MCInst.h:171
MCDisassembler::DecodeStatus DecodeStatus
static MCOperand createImm(int64_t Val)
Definition: MCInst.h:122
Target & getTheBPFTarget()