llvm/llvm/lib/Target/X86/X86IndirectBranchTracking.cpp

//===---- X86IndirectBranchTracking.cpp - Enables CET IBT mechanism -------===//
//
// 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 defines a pass that enables Indirect Branch Tracking (IBT) as part
// of Control-Flow Enforcement Technology (CET).
// The pass adds ENDBR (End Branch) machine instructions at the beginning of
// each basic block or function that is referenced by an indrect jump/call
// instruction.
// The ENDBR instructions have a NOP encoding and as such are ignored in
// targets that do not support CET IBT mechanism.
//===----------------------------------------------------------------------===//

#include "X86.h"
#include "X86InstrInfo.h"
#include "X86Subtarget.h"
#include "X86TargetMachine.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/IR/Module.h"

usingnamespacellvm;

#define DEBUG_TYPE …

cl::opt<bool> IndirectBranchTracking(
    "x86-indirect-branch-tracking", cl::init(false), cl::Hidden,
    cl::desc("Enable X86 indirect branch tracking pass."));

STATISTIC(NumEndBranchAdded, "Number of ENDBR instructions added");

namespace {
class X86IndirectBranchTrackingPass : public MachineFunctionPass { … };

} // end anonymous namespace

char X86IndirectBranchTrackingPass::ID = …;

FunctionPass *llvm::createX86IndirectBranchTrackingPass() { … }

bool X86IndirectBranchTrackingPass::addENDBR(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator I) const { … }

static bool IsCallReturnTwice(llvm::MachineOperand &MOp) { … }

// Checks if function should have an ENDBR in its prologue
static bool needsPrologueENDBR(MachineFunction &MF, const Module *M) { … }

bool X86IndirectBranchTrackingPass::runOnMachineFunction(MachineFunction &MF) { … }