1 //===-- BPFMCCodeEmitter.cpp - Convert BPF code to machine code -----------===//
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 implements the BPFMCCodeEmitter class.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "MCTargetDesc/BPFMCTargetDesc.h"
15 #include "llvm/MC/MCCodeEmitter.h"
16 #include "llvm/MC/MCFixup.h"
17 #include "llvm/MC/MCInst.h"
18 #include "llvm/MC/MCInstrInfo.h"
19 #include "llvm/MC/MCRegisterInfo.h"
20 #include "llvm/MC/MCSubtargetInfo.h"
21 #include "llvm/MC/MCSymbol.h"
22 #include "llvm/ADT/Statistic.h"
23 #include "llvm/Support/raw_ostream.h"
24 using namespace llvm;
25
26 #define DEBUG_TYPE "mccodeemitter"
27
28 namespace {
29 class BPFMCCodeEmitter : public MCCodeEmitter {
30 BPFMCCodeEmitter(const BPFMCCodeEmitter &) = delete;
31 void operator=(const BPFMCCodeEmitter &) = delete;
32 const MCRegisterInfo &MRI;
33
34 public:
BPFMCCodeEmitter(const MCRegisterInfo & mri)35 BPFMCCodeEmitter(const MCRegisterInfo &mri) : MRI(mri) {}
36
~BPFMCCodeEmitter()37 ~BPFMCCodeEmitter() {}
38
39 // getBinaryCodeForInstr - TableGen'erated function for getting the
40 // binary encoding for an instruction.
41 uint64_t getBinaryCodeForInstr(const MCInst &MI,
42 SmallVectorImpl<MCFixup> &Fixups,
43 const MCSubtargetInfo &STI) const;
44
45 // getMachineOpValue - Return binary encoding of operand. If the machin
46 // operand requires relocation, record the relocation and return zero.
47 unsigned getMachineOpValue(const MCInst &MI, const MCOperand &MO,
48 SmallVectorImpl<MCFixup> &Fixups,
49 const MCSubtargetInfo &STI) const;
50
51 uint64_t getMemoryOpValue(const MCInst &MI, unsigned Op,
52 SmallVectorImpl<MCFixup> &Fixups,
53 const MCSubtargetInfo &STI) const;
54
55 void EncodeInstruction(const MCInst &MI, raw_ostream &OS,
56 SmallVectorImpl<MCFixup> &Fixups,
57 const MCSubtargetInfo &STI) const override;
58 };
59 }
60
createBPFMCCodeEmitter(const MCInstrInfo & MCII,const MCRegisterInfo & MRI,MCContext & Ctx)61 MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII,
62 const MCRegisterInfo &MRI,
63 MCContext &Ctx) {
64 return new BPFMCCodeEmitter(MRI);
65 }
66
getMachineOpValue(const MCInst & MI,const MCOperand & MO,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const67 unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI,
68 const MCOperand &MO,
69 SmallVectorImpl<MCFixup> &Fixups,
70 const MCSubtargetInfo &STI) const {
71 if (MO.isReg())
72 return MRI.getEncodingValue(MO.getReg());
73 if (MO.isImm())
74 return static_cast<unsigned>(MO.getImm());
75
76 assert(MO.isExpr());
77
78 const MCExpr *Expr = MO.getExpr();
79
80 assert(Expr->getKind() == MCExpr::SymbolRef);
81
82 if (MI.getOpcode() == BPF::JAL)
83 // func call name
84 Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_4));
85 else if (MI.getOpcode() == BPF::LD_imm64)
86 Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_8));
87 else
88 // bb label
89 Fixups.push_back(MCFixup::Create(0, Expr, FK_PCRel_2));
90
91 return 0;
92 }
93
94 // Emit one byte through output stream
EmitByte(unsigned char C,unsigned & CurByte,raw_ostream & OS)95 void EmitByte(unsigned char C, unsigned &CurByte, raw_ostream &OS) {
96 OS << (char)C;
97 ++CurByte;
98 }
99
100 // Emit a series of bytes (little endian)
EmitLEConstant(uint64_t Val,unsigned Size,unsigned & CurByte,raw_ostream & OS)101 void EmitLEConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
102 raw_ostream &OS) {
103 assert(Size <= 8 && "size too big in emit constant");
104
105 for (unsigned i = 0; i != Size; ++i) {
106 EmitByte(Val & 255, CurByte, OS);
107 Val >>= 8;
108 }
109 }
110
111 // Emit a series of bytes (big endian)
EmitBEConstant(uint64_t Val,unsigned Size,unsigned & CurByte,raw_ostream & OS)112 void EmitBEConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
113 raw_ostream &OS) {
114 assert(Size <= 8 && "size too big in emit constant");
115
116 for (int i = (Size - 1) * 8; i >= 0; i -= 8)
117 EmitByte((Val >> i) & 255, CurByte, OS);
118 }
119
EncodeInstruction(const MCInst & MI,raw_ostream & OS,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const120 void BPFMCCodeEmitter::EncodeInstruction(const MCInst &MI, raw_ostream &OS,
121 SmallVectorImpl<MCFixup> &Fixups,
122 const MCSubtargetInfo &STI) const {
123 unsigned Opcode = MI.getOpcode();
124 // Keep track of the current byte being emitted
125 unsigned CurByte = 0;
126
127 if (Opcode == BPF::LD_imm64 || Opcode == BPF::LD_pseudo) {
128 uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
129 EmitByte(Value >> 56, CurByte, OS);
130 EmitByte(((Value >> 48) & 0xff), CurByte, OS);
131 EmitLEConstant(0, 2, CurByte, OS);
132 EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS);
133
134 const MCOperand &MO = MI.getOperand(1);
135 uint64_t Imm = MO.isImm() ? MO.getImm() : 0;
136 EmitByte(0, CurByte, OS);
137 EmitByte(0, CurByte, OS);
138 EmitLEConstant(0, 2, CurByte, OS);
139 EmitLEConstant(Imm >> 32, 4, CurByte, OS);
140 } else {
141 // Get instruction encoding and emit it
142 uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
143 EmitByte(Value >> 56, CurByte, OS);
144 EmitByte((Value >> 48) & 0xff, CurByte, OS);
145 EmitLEConstant((Value >> 32) & 0xffff, 2, CurByte, OS);
146 EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS);
147 }
148 }
149
150 // Encode BPF Memory Operand
getMemoryOpValue(const MCInst & MI,unsigned Op,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const151 uint64_t BPFMCCodeEmitter::getMemoryOpValue(const MCInst &MI, unsigned Op,
152 SmallVectorImpl<MCFixup> &Fixups,
153 const MCSubtargetInfo &STI) const {
154 uint64_t Encoding;
155 const MCOperand Op1 = MI.getOperand(1);
156 assert(Op1.isReg() && "First operand is not register.");
157 Encoding = MRI.getEncodingValue(Op1.getReg());
158 Encoding <<= 16;
159 MCOperand Op2 = MI.getOperand(2);
160 assert(Op2.isImm() && "Second operand is not immediate.");
161 Encoding |= Op2.getImm() & 0xffff;
162 return Encoding;
163 }
164
165 #include "BPFGenMCCodeEmitter.inc"
166