90 lines
3.0 KiB
C++
90 lines
3.0 KiB
C++
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//===-- BPFELFObjectWriter.cpp - BPF ELF Writer ---------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/BPFMCTargetDesc.h"
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#include "llvm/BinaryFormat/ELF.h"
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#include "llvm/MC/MCELFObjectWriter.h"
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#include "llvm/MC/MCFixup.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/ErrorHandling.h"
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#include <cstdint>
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using namespace llvm;
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namespace {
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class BPFELFObjectWriter : public MCELFObjectTargetWriter {
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public:
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BPFELFObjectWriter(uint8_t OSABI);
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~BPFELFObjectWriter() override = default;
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protected:
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unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
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const MCFixup &Fixup, bool IsPCRel) const override;
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};
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} // end anonymous namespace
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BPFELFObjectWriter::BPFELFObjectWriter(uint8_t OSABI)
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: MCELFObjectTargetWriter(/*Is64Bit*/ true, OSABI, ELF::EM_BPF,
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/*HasRelocationAddend*/ false) {}
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unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) const {
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// determine the type of the relocation
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switch (Fixup.getKind()) {
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default:
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llvm_unreachable("invalid fixup kind!");
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case FK_SecRel_8:
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return ELF::R_BPF_64_64;
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case FK_PCRel_4:
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case FK_SecRel_4:
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return ELF::R_BPF_64_32;
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case FK_Data_8:
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return ELF::R_BPF_64_64;
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case FK_Data_4:
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if (const MCSymbolRefExpr *A = Target.getSymA()) {
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const MCSymbol &Sym = A->getSymbol();
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if (Sym.isDefined()) {
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MCSection &Section = Sym.getSection();
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const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
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assert(SectionELF && "Null section for reloc symbol");
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unsigned Flags = SectionELF->getFlags();
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if (Sym.isTemporary()) {
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// .BTF.ext generates FK_Data_4 relocations for
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// insn offset by creating temporary labels.
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// The insn offset is within the code section and
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// already been fulfilled by applyFixup(). No
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// further relocation is needed.
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// The reloc symbol should be in text section.
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if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR))
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return ELF::R_BPF_NONE;
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} else {
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// .BTF generates FK_Data_4 relocations for variable
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// offset in DataSec kind. Similar to the above .BTF.ext
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// insn offset, no further relocation is needed.
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// The reloc symbol should be in data section.
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if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_WRITE))
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return ELF::R_BPF_NONE;
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}
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}
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}
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return ELF::R_BPF_64_32;
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}
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}
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std::unique_ptr<MCObjectTargetWriter>
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llvm::createBPFELFObjectWriter(uint8_t OSABI) {
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return std::make_unique<BPFELFObjectWriter>(OSABI);
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}
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