//===-- BPFAsmBackend.cpp - BPF Assembler Backend -------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// #include "MCTargetDesc/BPFMCFixups.h" #include "MCTargetDesc/BPFMCTargetDesc.h" #include "llvm/ADT/StringRef.h" #include "llvm/MC/MCAsmBackend.h" #include "llvm/MC/MCAssembler.h" #include "llvm/MC/MCContext.h" #include "llvm/MC/MCFixup.h" #include "llvm/MC/MCFixupKindInfo.h" #include "llvm/MC/MCObjectWriter.h" #include "llvm/Support/EndianStream.h" #include #include using namespace llvm; namespace { class BPFAsmBackend : public MCAsmBackend { public: BPFAsmBackend(llvm::endianness Endian) : MCAsmBackend(Endian) {} ~BPFAsmBackend() override = default; void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup, const MCValue &Target, MutableArrayRef Data, uint64_t Value, bool IsResolved, const MCSubtargetInfo *STI) const override; std::unique_ptr createObjectTargetWriter() const override; unsigned getNumFixupKinds() const override { return BPF::NumTargetFixupKinds; } const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override; bool writeNopData(raw_ostream &OS, uint64_t Count, const MCSubtargetInfo *STI) const override; }; } // end anonymous namespace const MCFixupKindInfo & BPFAsmBackend::getFixupKindInfo(MCFixupKind Kind) const { const static MCFixupKindInfo Infos[BPF::NumTargetFixupKinds] = { { "FK_BPF_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, }; if (Kind < FirstTargetFixupKind) return MCAsmBackend::getFixupKindInfo(Kind); assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() && "Invalid kind!"); return Infos[Kind - FirstTargetFixupKind]; } bool BPFAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count, const MCSubtargetInfo *STI) const { if ((Count % 8) != 0) return false; for (uint64_t i = 0; i < Count; i += 8) support::endian::write(OS, 0x15000000, Endian); return true; } void BPFAsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup, const MCValue &Target, MutableArrayRef Data, uint64_t Value, bool IsResolved, const MCSubtargetInfo *STI) const { if (Fixup.getKind() == FK_SecRel_8) { // The Value is 0 for global variables, and the in-section offset // for static variables. Write to the immediate field of the inst. assert(Value <= UINT32_MAX); support::endian::write(&Data[Fixup.getOffset() + 4], static_cast(Value), Endian); } else if (Fixup.getKind() == FK_Data_4) { support::endian::write(&Data[Fixup.getOffset()], Value, Endian); } else if (Fixup.getKind() == FK_Data_8) { support::endian::write(&Data[Fixup.getOffset()], Value, Endian); } else if (Fixup.getKind() == FK_PCRel_4) { Value = (uint32_t)((Value - 8) / 8); if (Endian == llvm::endianness::little) { Data[Fixup.getOffset() + 1] = 0x10; support::endian::write32le(&Data[Fixup.getOffset() + 4], Value); } else { Data[Fixup.getOffset() + 1] = 0x1; support::endian::write32be(&Data[Fixup.getOffset() + 4], Value); } } else if (Fixup.getTargetKind() == BPF::FK_BPF_PCRel_4) { // The input Value represents the number of bytes. Value = (uint32_t)((Value - 8) / 8); support::endian::write(&Data[Fixup.getOffset() + 4], Value, Endian); } else { assert(Fixup.getKind() == FK_PCRel_2); int64_t ByteOff = (int64_t)Value - 8; if (ByteOff > INT16_MAX * 8 || ByteOff < INT16_MIN * 8) report_fatal_error("Branch target out of insn range"); Value = (uint16_t)((Value - 8) / 8); support::endian::write(&Data[Fixup.getOffset() + 2], Value, Endian); } } std::unique_ptr BPFAsmBackend::createObjectTargetWriter() const { return createBPFELFObjectWriter(0); } MCAsmBackend *llvm::createBPFAsmBackend(const Target &T, const MCSubtargetInfo &STI, const MCRegisterInfo &MRI, const MCTargetOptions &) { return new BPFAsmBackend(llvm::endianness::little); } MCAsmBackend *llvm::createBPFbeAsmBackend(const Target &T, const MCSubtargetInfo &STI, const MCRegisterInfo &MRI, const MCTargetOptions &) { return new BPFAsmBackend(llvm::endianness::big); }