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 30 BPFAsmBackend(bool IsLittleEndian) 31 : MCAsmBackend(), IsLittleEndian(IsLittleEndian) {} 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 40 bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value, 41 const MCRelaxableFragment *DF, 42 const MCAsmLayout &Layout) const override { 43 return false; 44 } 45 46 unsigned getNumFixupKinds() const override { return 1; } 47 48 bool mayNeedRelaxation(const MCInst &Inst) const override { return false; } 49 50 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 56 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 66 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 92 MCObjectWriter *BPFAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const { 93 return createBPFELFObjectWriter(OS, 0, IsLittleEndian); 94 } 95 } 96 97 MCAsmBackend *llvm::createBPFAsmBackend(const Target &T, 98 const MCRegisterInfo &MRI, 99 const Triple &TT, StringRef CPU) { 100 return new BPFAsmBackend(/*IsLittleEndian=*/true); 101 } 102 103 MCAsmBackend *llvm::createBPFbeAsmBackend(const Target &T, 104 const MCRegisterInfo &MRI, 105 const Triple &TT, StringRef CPU) { 106 return new BPFAsmBackend(/*IsLittleEndian=*/false); 107 } 108
