llvm/llvm/lib/Target/ARM/ARMBranchTargets.cpp

//===-- ARMBranchTargets.cpp -- Harden code using v8.1-M BTI extension -----==//
//
// 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 pass inserts BTI instructions at the start of every function and basic
// block which could be indirectly called. The hardware will (when enabled)
// trap when an indirect branch or call instruction targets an instruction
// which is not a valid BTI instruction. This is intended to guard against
// control-flow hijacking attacks.
//
//===----------------------------------------------------------------------===//

#include "ARM.h"
#include "ARMInstrInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/Support/Debug.h"

usingnamespacellvm;

#define DEBUG_TYPE …
#define ARM_BRANCH_TARGETS_NAME …

namespace {
class ARMBranchTargets : public MachineFunctionPass { … };
} // end anonymous namespace

char ARMBranchTargets::ID = …;

INITIALIZE_PASS(…)

void ARMBranchTargets::getAnalysisUsage(AnalysisUsage &AU) const { … }

FunctionPass *llvm::createARMBranchTargetsPass() { … }

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

/// Insert a BTI/PACBTI instruction into a given basic block \c MBB. If
/// \c IsFirstBB is true (meaning that this is the first BB in a function) try
/// to find a PAC instruction and replace it with PACBTI. Otherwise just insert
/// a BTI instruction.
/// The point of insertion is in the beginning of the BB, immediately after meta
/// instructions (such labels in exception handling landing pads).
void ARMBranchTargets::addBTI(const ARMInstrInfo &TII, MachineBasicBlock &MBB,
                              bool IsFirstBB) { … }