llvm/llvm/lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp

//===-- MipsNaClELFStreamer.cpp - ELF Object Output for Mips NaCl ---------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements MCELFStreamer for Mips NaCl.  It emits .o object files
// as required by NaCl's SFI sandbox.  It inserts address-masking instructions
// before dangerous control-flow and memory access instructions.  It inserts
// address-masking instructions after instructions that change the stack
// pointer.  It ensures that the mask and the dangerous instruction are always
// emitted in the same bundle.  It aligns call + branch delay to the bundle end,
// so that return address is always aligned to the start of next bundle.
//
//===----------------------------------------------------------------------===//

#include "Mips.h"
#include "MipsELFStreamer.h"
#include "MipsMCNaCl.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCELFStreamer.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>

usingnamespacellvm;

#define DEBUG_TYPE …

namespace {

const unsigned IndirectBranchMaskReg = …;
const unsigned LoadStoreStackMaskReg = …;

/// Extend the generic MCELFStreamer class so that it can mask dangerous
/// instructions.

class MipsNaClELFStreamer : public MipsELFStreamer { … };

} // end anonymous namespace

namespace llvm {

bool isBasePlusOffsetMemoryAccess(unsigned Opcode, unsigned *AddrIdx,
                                  bool *IsStore) { … }

bool baseRegNeedsLoadStoreMask(unsigned Reg) { … }

MCELFStreamer *
createMipsNaClELFStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> TAB,
                          std::unique_ptr<MCObjectWriter> OW,
                          std::unique_ptr<MCCodeEmitter> Emitter) { … }

} // end namespace llvm