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StackProtector: ensure protection does not interfere with tail call frame #2704

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Merged
merged 1 commit into from
Mar 17, 2021
Merged

StackProtector: ensure protection does not interfere with tail call frame #2704

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27 changes: 23 additions & 4 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1691,16 +1691,35 @@ static bool MIIsInTerminatorSequence(const MachineInstr &MI) {
/// terminator, but additionally the copies that move the vregs into the
/// physical registers.
static MachineBasicBlock::iterator
FindSplitPointForStackProtector(MachineBasicBlock *BB) {
FindSplitPointForStackProtector(MachineBasicBlock *BB,
const TargetInstrInfo &TII) {
MachineBasicBlock::iterator SplitPoint = BB->getFirstTerminator();
//
if (SplitPoint == BB->begin())
return SplitPoint;

MachineBasicBlock::iterator Start = BB->begin();
MachineBasicBlock::iterator Previous = SplitPoint;
--Previous;

if (TII.isTailCall(*SplitPoint) &&
Previous->getOpcode() == TII.getCallFrameDestroyOpcode()) {
// Call frames cannot be nested, so if this frame is describing the tail
// call itself then we must insert before the sequence even starts. On the
// other hand, it could be an unrelated call in which case this tail call
// has to register moves of its own and should be the split point.
bool DifferentCall = false;
MachineBasicBlock::iterator I = Previous;
do {
--I;
if (I->isCall()) {
DifferentCall = true;
break;
}
} while(I->getOpcode() != TII.getCallFrameSetupOpcode());

return DifferentCall ? SplitPoint : I;
}

while (MIIsInTerminatorSequence(*Previous)) {
SplitPoint = Previous;
if (Previous == Start)
Expand Down Expand Up @@ -1740,7 +1759,7 @@ SelectionDAGISel::FinishBasicBlock() {
// Add load and check to the basicblock.
FuncInfo->MBB = ParentMBB;
FuncInfo->InsertPt =
FindSplitPointForStackProtector(ParentMBB);
FindSplitPointForStackProtector(ParentMBB, *TII);
SDB->visitSPDescriptorParent(SDB->SPDescriptor, ParentMBB);
CurDAG->setRoot(SDB->getRoot());
SDB->clear();
Expand All @@ -1759,7 +1778,7 @@ SelectionDAGISel::FinishBasicBlock() {
// register allocation issues caused by us splitting the parent mbb. The
// register allocator will clean up said virtual copies later on.
MachineBasicBlock::iterator SplitPoint =
FindSplitPointForStackProtector(ParentMBB);
FindSplitPointForStackProtector(ParentMBB, *TII);

// Splice the terminator of ParentMBB into SuccessMBB.
SuccessMBB->splice(SuccessMBB->end(), ParentMBB,
Expand Down
26 changes: 26 additions & 0 deletions llvm/test/CodeGen/X86/tailcc-ssp.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
; RUN: llc -mtriple=x86_64-windows-msvc %s -o - -verify-machineinstrs | FileCheck %s

declare void @h(i8*, i64, i8*)

define tailcc void @tailcall_frame(i8* %0, i64 %1) sspreq {
; CHECK-LABEL: tailcall_frame:
; CHECK: callq __security_check_cookie
; CHECK: xorl %ecx, %ecx
; CHECK: jmp h

tail call tailcc void @h(i8* null, i64 0, i8* null)
ret void
}

declare void @bar()
define void @tailcall_unrelated_frame() sspreq {
; CHECK-LABEL: tailcall_unrelated_frame:
; CHECK: subq [[STACK:\$.*]], %rsp
; CHECK: callq bar
; CHECK: callq __security_check_cookie
; CHECK: addq [[STACK]], %rsp
; CHECK: jmp bar
call void @bar()
tail call void @bar()
ret void
}