1283625Sdim//===-- BPFAsmBackend.cpp - BPF Assembler Backend -------------------------===// 2283625Sdim// 3353358Sdim// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4353358Sdim// See https://llvm.org/LICENSE.txt for license information. 5353358Sdim// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6283625Sdim// 7283625Sdim//===----------------------------------------------------------------------===// 8283625Sdim 9283625Sdim#include "MCTargetDesc/BPFMCTargetDesc.h" 10314564Sdim#include "llvm/ADT/StringRef.h" 11283625Sdim#include "llvm/MC/MCAsmBackend.h" 12341825Sdim#include "llvm/MC/MCAssembler.h" 13341825Sdim#include "llvm/MC/MCContext.h" 14314564Sdim#include "llvm/MC/MCFixup.h" 15283625Sdim#include "llvm/MC/MCObjectWriter.h" 16341825Sdim#include "llvm/Support/EndianStream.h" 17314564Sdim#include <cassert> 18314564Sdim#include <cstdint> 19283625Sdim 20283625Sdimusing namespace llvm; 21283625Sdim 22283625Sdimnamespace { 23314564Sdim 24283625Sdimclass BPFAsmBackend : public MCAsmBackend { 25283625Sdimpublic: 26341825Sdim BPFAsmBackend(support::endianness Endian) : MCAsmBackend(Endian) {} 27314564Sdim ~BPFAsmBackend() override = default; 28283625Sdim 29321369Sdim void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup, 30321369Sdim const MCValue &Target, MutableArrayRef<char> Data, 31341825Sdim uint64_t Value, bool IsResolved, 32341825Sdim const MCSubtargetInfo *STI) const override; 33283625Sdim 34341825Sdim std::unique_ptr<MCObjectTargetWriter> 35341825Sdim createObjectTargetWriter() const override; 36283625Sdim 37283625Sdim // No instruction requires relaxation 38283625Sdim bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value, 39283625Sdim const MCRelaxableFragment *DF, 40283625Sdim const MCAsmLayout &Layout) const override { 41283625Sdim return false; 42283625Sdim } 43283625Sdim 44283625Sdim unsigned getNumFixupKinds() const override { return 1; } 45283625Sdim 46341825Sdim bool mayNeedRelaxation(const MCInst &Inst, 47341825Sdim const MCSubtargetInfo &STI) const override { 48341825Sdim return false; 49341825Sdim } 50283625Sdim 51309124Sdim void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI, 52309124Sdim MCInst &Res) const override {} 53283625Sdim 54341825Sdim bool writeNopData(raw_ostream &OS, uint64_t Count) const override; 55283625Sdim}; 56283625Sdim 57314564Sdim} // end anonymous namespace 58314564Sdim 59341825Sdimbool BPFAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const { 60283625Sdim if ((Count % 8) != 0) 61283625Sdim return false; 62283625Sdim 63283625Sdim for (uint64_t i = 0; i < Count; i += 8) 64341825Sdim support::endian::write<uint64_t>(OS, 0x15000000, Endian); 65283625Sdim 66283625Sdim return true; 67283625Sdim} 68283625Sdim 69321369Sdimvoid BPFAsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup, 70321369Sdim const MCValue &Target, 71321369Sdim MutableArrayRef<char> Data, uint64_t Value, 72341825Sdim bool IsResolved, 73341825Sdim const MCSubtargetInfo *STI) const { 74283625Sdim if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) { 75353358Sdim // The Value is 0 for global variables, and the in-section offset 76353358Sdim // for static variables. Write to the immediate field of the inst. 77353358Sdim assert(Value <= UINT32_MAX); 78353358Sdim support::endian::write<uint32_t>(&Data[Fixup.getOffset() + 4], 79353358Sdim static_cast<uint32_t>(Value), 80353358Sdim Endian); 81341825Sdim } else if (Fixup.getKind() == FK_Data_4) { 82341825Sdim support::endian::write<uint32_t>(&Data[Fixup.getOffset()], Value, Endian); 83341825Sdim } else if (Fixup.getKind() == FK_Data_8) { 84341825Sdim support::endian::write<uint64_t>(&Data[Fixup.getOffset()], Value, Endian); 85327952Sdim } else if (Fixup.getKind() == FK_PCRel_4) { 86327952Sdim Value = (uint32_t)((Value - 8) / 8); 87341825Sdim if (Endian == support::little) { 88327952Sdim Data[Fixup.getOffset() + 1] = 0x10; 89327952Sdim support::endian::write32le(&Data[Fixup.getOffset() + 4], Value); 90327952Sdim } else { 91327952Sdim Data[Fixup.getOffset() + 1] = 0x1; 92327952Sdim support::endian::write32be(&Data[Fixup.getOffset() + 4], Value); 93327952Sdim } 94284236Sdim } else { 95296417Sdim assert(Fixup.getKind() == FK_PCRel_2); 96296417Sdim Value = (uint16_t)((Value - 8) / 8); 97341825Sdim support::endian::write<uint16_t>(&Data[Fixup.getOffset() + 2], Value, 98341825Sdim Endian); 99284236Sdim } 100283625Sdim} 101283625Sdim 102341825Sdimstd::unique_ptr<MCObjectTargetWriter> 103341825SdimBPFAsmBackend::createObjectTargetWriter() const { 104341825Sdim return createBPFELFObjectWriter(0); 105283625Sdim} 106283625Sdim 107283625SdimMCAsmBackend *llvm::createBPFAsmBackend(const Target &T, 108327952Sdim const MCSubtargetInfo &STI, 109284734Sdim const MCRegisterInfo &MRI, 110327952Sdim const MCTargetOptions &) { 111341825Sdim return new BPFAsmBackend(support::little); 112283625Sdim} 113284236Sdim 114284236SdimMCAsmBackend *llvm::createBPFbeAsmBackend(const Target &T, 115327952Sdim const MCSubtargetInfo &STI, 116284734Sdim const MCRegisterInfo &MRI, 117327952Sdim const MCTargetOptions &) { 118341825Sdim return new BPFAsmBackend(support::big); 119284236Sdim} 120