1 //===-- BPFAsmBackend.cpp - BPF Assembler Backend -------------------------===//
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/ADT/StringRef.h"
11 #include "llvm/MC/MCAsmBackend.h"
12 #include "llvm/MC/MCAssembler.h"
13 #include "llvm/MC/MCContext.h"
14 #include "llvm/MC/MCFixup.h"
15 #include "llvm/MC/MCObjectWriter.h"
16 #include "llvm/Support/EndianStream.h"
24 class BPFAsmBackend : public MCAsmBackend {
26 BPFAsmBackend(support::endianness Endian) : MCAsmBackend(Endian) {}
27 ~BPFAsmBackend() override = default;
29 void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
30 const MCValue &Target, MutableArrayRef<char> Data,
31 uint64_t Value, bool IsResolved,
32 const MCSubtargetInfo *STI) const override;
34 std::unique_ptr<MCObjectTargetWriter>
35 createObjectTargetWriter() const override;
37 // No instruction requires relaxation
38 bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
39 const MCRelaxableFragment *DF,
40 const MCAsmLayout &Layout) const override {
44 unsigned getNumFixupKinds() const override { return 1; }
46 bool mayNeedRelaxation(const MCInst &Inst,
47 const MCSubtargetInfo &STI) const override {
51 bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
54 } // end anonymous namespace
56 bool BPFAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
60 for (uint64_t i = 0; i < Count; i += 8)
61 support::endian::write<uint64_t>(OS, 0x15000000, Endian);
66 void BPFAsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
67 const MCValue &Target,
68 MutableArrayRef<char> Data, uint64_t Value,
70 const MCSubtargetInfo *STI) const {
71 if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) {
72 // The Value is 0 for global variables, and the in-section offset
73 // for static variables. Write to the immediate field of the inst.
74 assert(Value <= UINT32_MAX);
75 support::endian::write<uint32_t>(&Data[Fixup.getOffset() + 4],
76 static_cast<uint32_t>(Value),
78 } else if (Fixup.getKind() == FK_Data_4) {
79 support::endian::write<uint32_t>(&Data[Fixup.getOffset()], Value, Endian);
80 } else if (Fixup.getKind() == FK_Data_8) {
81 support::endian::write<uint64_t>(&Data[Fixup.getOffset()], Value, Endian);
82 } else if (Fixup.getKind() == FK_PCRel_4) {
83 Value = (uint32_t)((Value - 8) / 8);
84 if (Endian == support::little) {
85 Data[Fixup.getOffset() + 1] = 0x10;
86 support::endian::write32le(&Data[Fixup.getOffset() + 4], Value);
88 Data[Fixup.getOffset() + 1] = 0x1;
89 support::endian::write32be(&Data[Fixup.getOffset() + 4], Value);
92 assert(Fixup.getKind() == FK_PCRel_2);
93 Value = (uint16_t)((Value - 8) / 8);
94 support::endian::write<uint16_t>(&Data[Fixup.getOffset() + 2], Value,
99 std::unique_ptr<MCObjectTargetWriter>
100 BPFAsmBackend::createObjectTargetWriter() const {
101 return createBPFELFObjectWriter(0);
104 MCAsmBackend *llvm::createBPFAsmBackend(const Target &T,
105 const MCSubtargetInfo &STI,
106 const MCRegisterInfo &MRI,
107 const MCTargetOptions &) {
108 return new BPFAsmBackend(support::little);
111 MCAsmBackend *llvm::createBPFbeAsmBackend(const Target &T,
112 const MCSubtargetInfo &STI,
113 const MCRegisterInfo &MRI,
114 const MCTargetOptions &) {
115 return new BPFAsmBackend(support::big);