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, MCInst &Res) const override {} 51 52 bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override; 53 }; 54 55 bool BPFAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const { 56 if ((Count % 8) != 0) 57 return false; 58 59 for (uint64_t i = 0; i < Count; i += 8) 60 OW->write64(0x15000000); 61 62 return true; 63 } 64 65 void BPFAsmBackend::applyFixup(const MCFixup &Fixup, char *Data, 66 unsigned DataSize, uint64_t Value, 67 bool IsPCRel) const { 68 69 if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) { 70 assert(Value == 0); 71 } else if (Fixup.getKind() == FK_Data_4 || Fixup.getKind() == FK_Data_8) { 72 unsigned Size = Fixup.getKind() == FK_Data_4 ? 4 : 8; 73 74 for (unsigned i = 0; i != Size; ++i) { 75 unsigned Idx = IsLittleEndian ? i : Size - i; 76 Data[Fixup.getOffset() + Idx] = uint8_t(Value >> (i * 8)); 77 } 78 } else { 79 assert(Fixup.getKind() == FK_PCRel_2); 80 Value = (uint16_t)((Value - 8) / 8); 81 if (IsLittleEndian) { 82 Data[Fixup.getOffset() + 2] = Value & 0xFF; 83 Data[Fixup.getOffset() + 3] = Value >> 8; 84 } else { 85 Data[Fixup.getOffset() + 2] = Value >> 8; 86 Data[Fixup.getOffset() + 3] = Value & 0xFF; 87 } 88 } 89 } 90 91 MCObjectWriter *BPFAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const { 92 return createBPFELFObjectWriter(OS, 0, IsLittleEndian); 93 } 94 } 95 96 MCAsmBackend *llvm::createBPFAsmBackend(const Target &T, 97 const MCRegisterInfo &MRI, 98 const Triple &TT, StringRef CPU) { 99 return new BPFAsmBackend(/*IsLittleEndian=*/true); 100 } 101 102 MCAsmBackend *llvm::createBPFbeAsmBackend(const Target &T, 103 const MCRegisterInfo &MRI, 104 const Triple &TT, StringRef CPU) { 105 return new BPFAsmBackend(/*IsLittleEndian=*/false); 106 } 107
