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 BPFAsmBackend() : MCAsmBackend() {} 29 ~BPFAsmBackend() override {} 30 31 void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize, 32 uint64_t Value, bool IsPCRel) const override; 33 34 MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override; 35 36 // No instruction requires relaxation 37 bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value, 38 const MCRelaxableFragment *DF, 39 const MCAsmLayout &Layout) const override { 40 return false; 41 } 42 43 unsigned getNumFixupKinds() const override { return 1; } 44 45 bool mayNeedRelaxation(const MCInst &Inst) const override { return false; } 46 47 void relaxInstruction(const MCInst &Inst, MCInst &Res) const override {} 48 49 bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override; 50 }; 51 52 bool BPFAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const { 53 if ((Count % 8) != 0) 54 return false; 55 56 for (uint64_t i = 0; i < Count; i += 8) 57 OW->Write64(0x15000000); 58 59 return true; 60 } 61 62 void BPFAsmBackend::applyFixup(const MCFixup &Fixup, char *Data, 63 unsigned DataSize, uint64_t Value, 64 bool IsPCRel) const { 65 66 if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) { 67 assert(Value == 0); 68 return; 69 } 70 assert(Fixup.getKind() == FK_PCRel_2); 71 *(uint16_t *)&Data[Fixup.getOffset() + 2] = (uint16_t)((Value - 8) / 8); 72 } 73 74 MCObjectWriter *BPFAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const { 75 return createBPFELFObjectWriter(OS, 0); 76 } 77 } 78 79 MCAsmBackend *llvm::createBPFAsmBackend(const Target &T, 80 const MCRegisterInfo &MRI, StringRef TT, 81 StringRef CPU) { 82 return new BPFAsmBackend(); 83 } 84
