1 //===-- BPFAsmBackend.cpp - BPF Assembler Backend -------------------------===//
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 #include "MCTargetDesc/BPFMCTargetDesc.h"
11 #include "llvm/MC/MCAsmBackend.h"
12 #include "llvm/MC/MCAssembler.h"
13 #include "llvm/MC/MCDirectives.h"
14 #include "llvm/MC/MCELFObjectWriter.h"
15 #include "llvm/MC/MCFixupKindInfo.h"
16 #include "llvm/MC/MCObjectWriter.h"
17 #include "llvm/MC/MCSubtargetInfo.h"
18 #include "llvm/MC/MCExpr.h"
19 #include "llvm/MC/MCSymbol.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include "llvm/Support/raw_ostream.h"
22
23 using namespace llvm;
24
25 namespace {
26 class BPFAsmBackend : public MCAsmBackend {
27 public:
28 bool IsLittleEndian;
29
BPFAsmBackend(bool IsLittleEndian)30 BPFAsmBackend(bool IsLittleEndian)
31 : MCAsmBackend(), IsLittleEndian(IsLittleEndian) {}
~BPFAsmBackend()32 ~BPFAsmBackend() override {}
33
34 void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
35 uint64_t Value, bool IsPCRel) const override;
36
37 MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override;
38
39 // No instruction requires relaxation
fixupNeedsRelaxation(const MCFixup & Fixup,uint64_t Value,const MCRelaxableFragment * DF,const MCAsmLayout & Layout) const40 bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
41 const MCRelaxableFragment *DF,
42 const MCAsmLayout &Layout) const override {
43 return false;
44 }
45
getNumFixupKinds() const46 unsigned getNumFixupKinds() const override { return 1; }
47
mayNeedRelaxation(const MCInst & Inst) const48 bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
49
relaxInstruction(const MCInst & Inst,const MCSubtargetInfo & STI,MCInst & Res) const50 void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
51 MCInst &Res) const override {}
52
53 bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
54 };
55
writeNopData(uint64_t Count,MCObjectWriter * OW) const56 bool BPFAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
57 if ((Count % 8) != 0)
58 return false;
59
60 for (uint64_t i = 0; i < Count; i += 8)
61 OW->write64(0x15000000);
62
63 return true;
64 }
65
applyFixup(const MCFixup & Fixup,char * Data,unsigned DataSize,uint64_t Value,bool IsPCRel) const66 void BPFAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
67 unsigned DataSize, uint64_t Value,
68 bool IsPCRel) const {
69
70 if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) {
71 assert(Value == 0);
72 } else if (Fixup.getKind() == FK_Data_4 || Fixup.getKind() == FK_Data_8) {
73 unsigned Size = Fixup.getKind() == FK_Data_4 ? 4 : 8;
74
75 for (unsigned i = 0; i != Size; ++i) {
76 unsigned Idx = IsLittleEndian ? i : Size - i;
77 Data[Fixup.getOffset() + Idx] = uint8_t(Value >> (i * 8));
78 }
79 } else {
80 assert(Fixup.getKind() == FK_PCRel_2);
81 Value = (uint16_t)((Value - 8) / 8);
82 if (IsLittleEndian) {
83 Data[Fixup.getOffset() + 2] = Value & 0xFF;
84 Data[Fixup.getOffset() + 3] = Value >> 8;
85 } else {
86 Data[Fixup.getOffset() + 2] = Value >> 8;
87 Data[Fixup.getOffset() + 3] = Value & 0xFF;
88 }
89 }
90 }
91
createObjectWriter(raw_pwrite_stream & OS) const92 MCObjectWriter *BPFAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
93 return createBPFELFObjectWriter(OS, 0, IsLittleEndian);
94 }
95 }
96
createBPFAsmBackend(const Target & T,const MCRegisterInfo & MRI,const Triple & TT,StringRef CPU)97 MCAsmBackend *llvm::createBPFAsmBackend(const Target &T,
98 const MCRegisterInfo &MRI,
99 const Triple &TT, StringRef CPU) {
100 return new BPFAsmBackend(/*IsLittleEndian=*/true);
101 }
102
createBPFbeAsmBackend(const Target & T,const MCRegisterInfo & MRI,const Triple & TT,StringRef CPU)103 MCAsmBackend *llvm::createBPFbeAsmBackend(const Target &T,
104 const MCRegisterInfo &MRI,
105 const Triple &TT, StringRef CPU) {
106 return new BPFAsmBackend(/*IsLittleEndian=*/false);
107 }
108