1 //===-- BPFELFObjectWriter.cpp - BPF ELF Writer ---------------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 #include "MCTargetDesc/BPFMCTargetDesc.h"
10 #include "llvm/BinaryFormat/ELF.h"
11 #include "llvm/MC/MCELFObjectWriter.h"
12 #include "llvm/MC/MCFixup.h"
13 #include "llvm/MC/MCObjectWriter.h"
14 #include "llvm/MC/MCValue.h"
15 #include "llvm/Support/ErrorHandling.h"
22 class BPFELFObjectWriter : public MCELFObjectTargetWriter {
24 BPFELFObjectWriter(uint8_t OSABI);
25 ~BPFELFObjectWriter() override = default;
28 unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
29 const MCFixup &Fixup, bool IsPCRel) const override;
32 } // end anonymous namespace
34 BPFELFObjectWriter::BPFELFObjectWriter(uint8_t OSABI)
35 : MCELFObjectTargetWriter(/*Is64Bit*/ true, OSABI, ELF::EM_BPF,
36 /*HasRelocationAddend*/ false) {}
38 unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
41 // determine the type of the relocation
42 switch (Fixup.getKind()) {
44 llvm_unreachable("invalid fixup kind!");
46 return ELF::R_BPF_64_64;
49 return ELF::R_BPF_64_32;
51 return ELF::R_BPF_64_64;
53 if (const MCSymbolRefExpr *A = Target.getSymA()) {
54 const MCSymbol &Sym = A->getSymbol();
56 if (Sym.isDefined()) {
57 MCSection &Section = Sym.getSection();
58 const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
59 assert(SectionELF && "Null section for reloc symbol");
61 unsigned Flags = SectionELF->getFlags();
63 if (Sym.isTemporary()) {
64 // .BTF.ext generates FK_Data_4 relocations for
65 // insn offset by creating temporary labels.
66 // The insn offset is within the code section and
67 // already been fulfilled by applyFixup(). No
68 // further relocation is needed.
69 // The reloc symbol should be in text section.
70 if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR))
71 return ELF::R_BPF_NONE;
73 // .BTF generates FK_Data_4 relocations for variable
74 // offset in DataSec kind. Similar to the above .BTF.ext
75 // insn offset, no further relocation is needed.
76 // The reloc symbol should be in data section.
77 if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_WRITE))
78 return ELF::R_BPF_NONE;
82 return ELF::R_BPF_64_32;
86 std::unique_ptr<MCObjectTargetWriter>
87 llvm::createBPFELFObjectWriter(uint8_t OSABI) {
88 return std::make_unique<BPFELFObjectWriter>(OSABI);