1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89
|
//===-- BPFELFObjectWriter.cpp - BPF ELF Writer ---------------------------===//
//
// 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/BPFMCTargetDesc.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/ErrorHandling.h"
#include <cstdint>
using namespace llvm;
namespace {
class BPFELFObjectWriter : public MCELFObjectTargetWriter {
public:
BPFELFObjectWriter(uint8_t OSABI);
~BPFELFObjectWriter() override = default;
protected:
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
};
} // end anonymous namespace
BPFELFObjectWriter::BPFELFObjectWriter(uint8_t OSABI)
: MCELFObjectTargetWriter(/*Is64Bit*/ true, OSABI, ELF::EM_BPF,
/*HasRelocationAddend*/ false) {}
unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const {
// determine the type of the relocation
switch ((unsigned)Fixup.getKind()) {
default:
llvm_unreachable("invalid fixup kind!");
case FK_SecRel_8:
return ELF::R_BPF_64_64;
case FK_PCRel_4:
case FK_SecRel_4:
return ELF::R_BPF_64_32;
case FK_Data_8:
return ELF::R_BPF_64_64;
case FK_Data_4:
if (const MCSymbolRefExpr *A = Target.getSymA()) {
const MCSymbol &Sym = A->getSymbol();
if (Sym.isDefined()) {
MCSection &Section = Sym.getSection();
const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
assert(SectionELF && "Null section for reloc symbol");
unsigned Flags = SectionELF->getFlags();
if (Sym.isTemporary()) {
// .BTF.ext generates FK_Data_4 relocations for
// insn offset by creating temporary labels.
// The insn offset is within the code section and
// already been fulfilled by applyFixup(). No
// further relocation is needed.
// The reloc symbol should be in text section.
if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR))
return ELF::R_BPF_NONE;
} else {
// .BTF generates FK_Data_4 relocations for variable
// offset in DataSec kind. Similar to the above .BTF.ext
// insn offset, no further relocation is needed.
// The reloc symbol should be in data section.
if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_WRITE))
return ELF::R_BPF_NONE;
}
}
}
return ELF::R_BPF_64_32;
}
}
std::unique_ptr<MCObjectTargetWriter>
llvm::createBPFELFObjectWriter(uint8_t OSABI) {
return llvm::make_unique<BPFELFObjectWriter>(OSABI);
}
|