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119 lines
4.0 KiB
C++
119 lines
4.0 KiB
C++
//===-- BPFAsmBackend.cpp - BPF Assembler Backend -------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/BPFMCTargetDesc.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCFixup.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include <cassert>
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#include <cstdint>
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using namespace llvm;
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namespace {
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class BPFAsmBackend : public MCAsmBackend {
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public:
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bool IsLittleEndian;
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BPFAsmBackend(bool IsLittleEndian)
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: MCAsmBackend(), IsLittleEndian(IsLittleEndian) {}
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~BPFAsmBackend() override = default;
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void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
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const MCValue &Target, MutableArrayRef<char> Data,
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uint64_t Value, bool IsResolved) const override;
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std::unique_ptr<MCObjectWriter>
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createObjectWriter(raw_pwrite_stream &OS) const override;
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// No instruction requires relaxation
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bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
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const MCRelaxableFragment *DF,
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const MCAsmLayout &Layout) const override {
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return false;
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}
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unsigned getNumFixupKinds() const override { return 1; }
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bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
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void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
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MCInst &Res) const override {}
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bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
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};
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} // end anonymous namespace
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bool BPFAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
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if ((Count % 8) != 0)
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return false;
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for (uint64_t i = 0; i < Count; i += 8)
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OW->write64(0x15000000);
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return true;
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}
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void BPFAsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
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const MCValue &Target,
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MutableArrayRef<char> Data, uint64_t Value,
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bool IsResolved) const {
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if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) {
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assert(Value == 0);
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} else if (Fixup.getKind() == FK_Data_4 || Fixup.getKind() == FK_Data_8) {
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unsigned Size = Fixup.getKind() == FK_Data_4 ? 4 : 8;
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for (unsigned i = 0; i != Size; ++i) {
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unsigned Idx = IsLittleEndian ? i : Size - i - 1;
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Data[Fixup.getOffset() + Idx] = uint8_t(Value >> (i * 8));
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}
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} else if (Fixup.getKind() == FK_PCRel_4) {
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Value = (uint32_t)((Value - 8) / 8);
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if (IsLittleEndian) {
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Data[Fixup.getOffset() + 1] = 0x10;
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support::endian::write32le(&Data[Fixup.getOffset() + 4], Value);
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} else {
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Data[Fixup.getOffset() + 1] = 0x1;
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support::endian::write32be(&Data[Fixup.getOffset() + 4], Value);
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}
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} else {
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assert(Fixup.getKind() == FK_PCRel_2);
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Value = (uint16_t)((Value - 8) / 8);
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if (IsLittleEndian) {
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Data[Fixup.getOffset() + 2] = Value & 0xFF;
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Data[Fixup.getOffset() + 3] = Value >> 8;
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} else {
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Data[Fixup.getOffset() + 2] = Value >> 8;
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Data[Fixup.getOffset() + 3] = Value & 0xFF;
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}
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}
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}
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std::unique_ptr<MCObjectWriter>
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BPFAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
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return createBPFELFObjectWriter(OS, 0, IsLittleEndian);
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}
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MCAsmBackend *llvm::createBPFAsmBackend(const Target &T,
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const MCSubtargetInfo &STI,
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const MCRegisterInfo &MRI,
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const MCTargetOptions &) {
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return new BPFAsmBackend(/*IsLittleEndian=*/true);
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}
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MCAsmBackend *llvm::createBPFbeAsmBackend(const Target &T,
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const MCSubtargetInfo &STI,
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const MCRegisterInfo &MRI,
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const MCTargetOptions &) {
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return new BPFAsmBackend(/*IsLittleEndian=*/false);
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}
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