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[X86] Fix to X86LoadValueInjectionRetHardeningPass for possible segfault
ClosedPublic

Authored by sconstab on Apr 6 2020, 1:29 PM.

Reviewers

craig.topper

Commits

Summary

MBB.back() could segfault if MBB.empty(). Fixed by checking for MBB.empty() in the loop.

LGTM

This revision is now accepted and ready to land.Apr 6 2020, 1:44 PM

@craig.topper Anyone else I should add as a reviewer? Or can we just go ahead and merge?

This revision was not accepted when it landed; it landed in state Needs Review.Apr 10 2020, 6:51 PM

This revision was automatically updated to reflect the committed changes.

Path

Size

llvm/

lib/

Target/

X86/

3 lines

Show First 20 Lines • Show All 93 Lines • ▼ Show 20 Lines	LLVM_DEBUG(dbgs() << "Selected register "
<< Subtarget->getRegisterInfo()->getRegAsmName(ClobberReg)		<< Subtarget->getRegisterInfo()->getRegAsmName(ClobberReg)
<< " to clobber\n");		<< " to clobber\n");
} else {		} else {
LLVM_DEBUG(dbgs() << "Could not find a register to clobber\n");		LLVM_DEBUG(dbgs() << "Could not find a register to clobber\n");
}		}

bool Modified = false;		bool Modified = false;
for (auto &MBB : MF) {		for (auto &MBB : MF) {
		if (MBB.empty())
		continue;

MachineInstr &MI = MBB.back();		MachineInstr &MI = MBB.back();
if (MI.getOpcode() != X86::RETQ)		if (MI.getOpcode() != X86::RETQ)
continue;		continue;

if (ClobberReg != X86::NoRegister) {		if (ClobberReg != X86::NoRegister) {
MBB.erase_instr(&MI);		MBB.erase_instr(&MI);
BuildMI(MBB, MBB.end(), DebugLoc(), TII->get(X86::POP64r))		BuildMI(MBB, MBB.end(), DebugLoc(), TII->get(X86::POP64r))
.addReg(ClobberReg, RegState::Define)		.addReg(ClobberReg, RegState::Define)
Show All 31 Lines