d3589edafc
`Data` now references the first byte of the fixup offset within the current fragment. MCAssembler::layout asserts that the fixup offset is within either the fixed-size content or the optional variable-size tail, as this is the most the generic code can validate without knowing the target-specific fixup size. Many backends applyFixup assert ``` assert(Offset + Size <= F.getSize() && "Invalid fixup offset!"); ``` This refactoring allows a subsequent change to move the fixed-size content outside of MCSection::ContentStorage, fixing the -fsanitize=pointer-overflow issue of #150846 Pull Request: https://github.com/llvm/llvm-project/pull/151724
124 lines
4.4 KiB
C++
124 lines
4.4 KiB
C++
//===-- BPFAsmBackend.cpp - BPF Assembler Backend -------------------------===//
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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/BPFMCFixups.h"
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#include "MCTargetDesc/BPFMCTargetDesc.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.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/Support/EndianStream.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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BPFAsmBackend(llvm::endianness Endian) : MCAsmBackend(Endian) {}
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~BPFAsmBackend() override = default;
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void applyFixup(const MCFragment &, const MCFixup &, const MCValue &Target,
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uint8_t *Data, uint64_t Value, bool IsResolved) override;
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std::unique_ptr<MCObjectTargetWriter>
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createObjectTargetWriter() const override;
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MCFixupKindInfo getFixupKindInfo(MCFixupKind Kind) const override;
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bool writeNopData(raw_ostream &OS, uint64_t Count,
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const MCSubtargetInfo *STI) const override;
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};
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} // end anonymous namespace
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MCFixupKindInfo BPFAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
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const static MCFixupKindInfo Infos[BPF::NumTargetFixupKinds] = {
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{"FK_BPF_PCRel_4", 0, 32, 0},
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};
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if (Kind < FirstTargetFixupKind)
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return MCAsmBackend::getFixupKindInfo(Kind);
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assert(unsigned(Kind - FirstTargetFixupKind) < BPF::NumTargetFixupKinds &&
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"Invalid kind!");
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return Infos[Kind - FirstTargetFixupKind];
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}
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bool BPFAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count,
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const MCSubtargetInfo *STI) 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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support::endian::write<uint64_t>(OS, 0x15000000, Endian);
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return true;
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}
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void BPFAsmBackend::applyFixup(const MCFragment &F, const MCFixup &Fixup,
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const MCValue &Target, uint8_t *Data,
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uint64_t Value, bool IsResolved) {
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maybeAddReloc(F, Fixup, Target, Value, IsResolved);
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if (Fixup.getKind() == FK_SecRel_8) {
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// The Value is 0 for global variables, and the in-section offset
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// for static variables. Write to the immediate field of the inst.
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assert(Value <= UINT32_MAX);
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support::endian::write<uint32_t>(Data + 4, static_cast<uint32_t>(Value),
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Endian);
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} else if (Fixup.getKind() == FK_Data_4 && !Fixup.isPCRel()) {
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support::endian::write<uint32_t>(Data, Value, Endian);
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} else if (Fixup.getKind() == FK_Data_8) {
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support::endian::write<uint64_t>(Data, Value, Endian);
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} else if (Fixup.getKind() == FK_Data_4 && Fixup.isPCRel()) {
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Value = (uint32_t)((Value - 8) / 8);
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if (Endian == llvm::endianness::little) {
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Data[1] = 0x10;
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support::endian::write32le(Data + 4, Value);
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} else {
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Data[1] = 0x1;
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support::endian::write32be(Data + 4, Value);
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}
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} else if (Fixup.getKind() == BPF::FK_BPF_PCRel_4) {
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// The input Value represents the number of bytes.
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Value = (uint32_t)((Value - 8) / 8);
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support::endian::write<uint32_t>(Data + 4, Value, Endian);
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} else {
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assert(Fixup.getKind() == FK_Data_2 && Fixup.isPCRel());
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int64_t ByteOff = (int64_t)Value - 8;
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if (ByteOff > INT16_MAX * 8 || ByteOff < INT16_MIN * 8)
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report_fatal_error("Branch target out of insn range");
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Value = (uint16_t)((Value - 8) / 8);
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support::endian::write<uint16_t>(Data + 2, Value, Endian);
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}
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}
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std::unique_ptr<MCObjectTargetWriter>
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BPFAsmBackend::createObjectTargetWriter() const {
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return createBPFELFObjectWriter(0);
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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(llvm::endianness::little);
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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(llvm::endianness::big);
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}
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