LLVM  7.0.0svn
BPFDisassembler.cpp
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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"
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/MC/MCAsmInfo.h"
19 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCInst.h"
25 #include <cstdint>
26 
27 using namespace llvm;
28 
29 #define DEBUG_TYPE "bpf-disassembler"
30 
32 
33 namespace {
34 
35 /// A disassembler class for BPF.
36 class BPFDisassembler : public MCDisassembler {
37 public:
38  enum BPF_CLASS {
39  BPF_LD = 0x0,
40  BPF_LDX = 0x1,
41  BPF_ST = 0x2,
42  BPF_STX = 0x3,
43  BPF_ALU = 0x4,
44  BPF_JMP = 0x5,
45  BPF_RES = 0x6,
46  BPF_ALU64 = 0x7
47  };
48 
49  enum BPF_SIZE {
50  BPF_W = 0x0,
51  BPF_H = 0x1,
52  BPF_B = 0x2,
53  BPF_DW = 0x3
54  };
55 
56  enum BPF_MODE {
57  BPF_IMM = 0x0,
58  BPF_ABS = 0x1,
59  BPF_IND = 0x2,
60  BPF_MEM = 0x3,
61  BPF_LEN = 0x4,
62  BPF_MSH = 0x5,
63  BPF_XADD = 0x6
64  };
65 
66  BPFDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
67  : MCDisassembler(STI, Ctx) {}
68  ~BPFDisassembler() override = default;
69 
70  DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
71  ArrayRef<uint8_t> Bytes, uint64_t Address,
72  raw_ostream &VStream,
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 namespace
81 
83  const MCSubtargetInfo &STI,
84  MCContext &Ctx) {
85  return new BPFDisassembler(STI, Ctx);
86 }
87 
88 
89 extern "C" void LLVMInitializeBPFDisassembler() {
90  // Register the disassembler.
97 }
98 
99 static 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 
103 static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo,
104  uint64_t /*Address*/,
105  const void * /*Decoder*/) {
106  if (RegNo > 11)
107  return MCDisassembler::Fail;
108 
109  unsigned Reg = GPRDecoderTable[RegNo];
110  Inst.addOperand(MCOperand::createReg(Reg));
112 }
113 
114 static 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 
118 static DecodeStatus DecodeGPR32RegisterClass(MCInst &Inst, unsigned RegNo,
119  uint64_t /*Address*/,
120  const void * /*Decoder*/) {
121  if (RegNo > 11)
122  return MCDisassembler::Fail;
123 
124  unsigned Reg = GPR32DecoderTable[RegNo];
125  Inst.addOperand(MCOperand::createReg(Reg));
127 }
128 
129 static DecodeStatus decodeMemoryOpValue(MCInst &Inst, unsigned Insn,
130  uint64_t Address, const void *Decoder) {
131  unsigned Register = (Insn >> 16) & 0xf;
132  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
133  unsigned Offset = (Insn & 0xffff);
134  Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset)));
135 
137 }
138 
139 #include "BPFGenDisassemblerTables.inc"
141  uint64_t &Size, uint64_t &Insn,
142  bool IsLittleEndian) {
143  uint64_t Lo, Hi;
144 
145  if (Bytes.size() < 8) {
146  Size = 0;
147  return MCDisassembler::Fail;
148  }
149 
150  Size = 8;
151  if (IsLittleEndian) {
152  Hi = (Bytes[0] << 24) | (Bytes[1] << 16) | (Bytes[2] << 0) | (Bytes[3] << 8);
153  Lo = (Bytes[4] << 0) | (Bytes[5] << 8) | (Bytes[6] << 16) | (Bytes[7] << 24);
154  } else {
155  Hi = (Bytes[0] << 24) | ((Bytes[1] & 0x0F) << 20) | ((Bytes[1] & 0xF0) << 12) |
156  (Bytes[2] << 8) | (Bytes[3] << 0);
157  Lo = (Bytes[4] << 24) | (Bytes[5] << 16) | (Bytes[6] << 8) | (Bytes[7] << 0);
158  }
159  Insn = Make_64(Hi, Lo);
160 
162 }
163 
164 DecodeStatus BPFDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
165  ArrayRef<uint8_t> Bytes,
166  uint64_t Address,
167  raw_ostream &VStream,
168  raw_ostream &CStream) const {
169  bool IsLittleEndian = getContext().getAsmInfo()->isLittleEndian();
170  uint64_t Insn, Hi;
171  DecodeStatus Result;
172 
173  Result = readInstruction64(Bytes, Address, Size, Insn, IsLittleEndian);
174  if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
175 
176  uint8_t InstClass = getInstClass(Insn);
177  if ((InstClass == BPF_LDX || InstClass == BPF_STX) &&
178  getInstSize(Insn) != BPF_DW &&
179  getInstMode(Insn) == BPF_MEM &&
180  STI.getFeatureBits()[BPF::ALU32])
181  Result = decodeInstruction(DecoderTableBPFALU3264, Instr, Insn, Address,
182  this, STI);
183  else
184  Result = decodeInstruction(DecoderTableBPF64, Instr, Insn, Address, this,
185  STI);
186 
187  if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
188 
189  switch (Instr.getOpcode()) {
190  case BPF::LD_imm64:
191  case BPF::LD_pseudo: {
192  if (Bytes.size() < 16) {
193  Size = 0;
194  return MCDisassembler::Fail;
195  }
196  Size = 16;
197  if (IsLittleEndian)
198  Hi = (Bytes[12] << 0) | (Bytes[13] << 8) | (Bytes[14] << 16) | (Bytes[15] << 24);
199  else
200  Hi = (Bytes[12] << 24) | (Bytes[13] << 16) | (Bytes[14] << 8) | (Bytes[15] << 0);
201  auto& Op = Instr.getOperand(1);
202  Op.setImm(Make_64(Hi, Op.getImm()));
203  break;
204  }
205  case BPF::LD_ABS_B:
206  case BPF::LD_ABS_H:
207  case BPF::LD_ABS_W:
208  case BPF::LD_IND_B:
209  case BPF::LD_IND_H:
210  case BPF::LD_IND_W: {
211  auto Op = Instr.getOperand(0);
212  Instr.clear();
214  Instr.addOperand(Op);
215  break;
216  }
217  }
218 
219  return Result;
220 }
221 
222 typedef DecodeStatus (*DecodeFunc)(MCInst &MI, unsigned insn, uint64_t Address,
223  const void *Decoder);
#define R4(n)
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
void clear()
Definition: MCInst.h:191
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:116
Context object for machine code objects.
Definition: MCContext.h:63
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:161
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:149
#define R6(n)
static MCDisassembler * createBPFDisassembler(const Target &T, const MCSubtargetInfo &STI, MCContext &Ctx)
const MCOperand & getOperand(unsigned i) const
Definition: MCInst.h:182
Promote Memory to Register
Definition: Mem2Reg.cpp:110
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.
Target & getTheBPFleTarget()
static DecodeStatus DecodeGPR32RegisterClass(MCInst &Inst, unsigned RegNo, uint64_t, const void *)
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
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:294
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:46
IRTranslator LLVM IR MI
void addOperand(const MCOperand &Op)
Definition: MCInst.h:186
static const unsigned GPR32DecoderTable[]
Target & getTheBPFbeTarget()
unsigned getOpcode() const
Definition: MCInst.h:174
MCDisassembler::DecodeStatus DecodeStatus
static MCOperand createImm(int64_t Val)
Definition: MCInst.h:123
Target & getTheBPFTarget()