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[X86] Fix SLH crash on llvm.eh.sjlh.longjmp #77959

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Merged
merged 2 commits into from
Jan 14, 2024
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[X86] Fix SLH crash on llvm.eh.sjlh.longjmp #77959

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61c15f9
[X86] Fix SLH crash on llvm.eh.sjlh.longjmp
nmosier Jan 12, 2024
ef2bbf1
Move Reg.isVirtual() check into canHardenRegister() and remove redund…
nmosier Jan 13, 2024
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7 changes: 5 additions & 2 deletions llvm/lib/Target/X86/X86SpeculativeLoadHardening.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1840,7 +1840,7 @@ MachineInstr *X86SpeculativeLoadHardeningPass::sinkPostLoadHardenedInst(
// just bail. Also check that its register class is one of the ones we
// can harden.
Register UseDefReg = UseMI.getOperand(0).getReg();
if (!UseDefReg.isVirtual() || !canHardenRegister(UseDefReg))
if (!canHardenRegister(UseDefReg))
return {};

SingleUseMI = &UseMI;
Expand All @@ -1863,6 +1863,10 @@ MachineInstr *X86SpeculativeLoadHardeningPass::sinkPostLoadHardenedInst(
}

bool X86SpeculativeLoadHardeningPass::canHardenRegister(Register Reg) {
// We only support hardening virtual registers.
if (!Reg.isVirtual())
return false;

auto *RC = MRI->getRegClass(Reg);
int RegBytes = TRI->getRegSizeInBits(*RC) / 8;
if (RegBytes > 8)
Expand Down Expand Up @@ -1909,7 +1913,6 @@ unsigned X86SpeculativeLoadHardeningPass::hardenValueInRegister(
Register Reg, MachineBasicBlock &MBB, MachineBasicBlock::iterator InsertPt,
const DebugLoc &Loc) {
assert(canHardenRegister(Reg) && "Cannot harden this register!");
assert(Reg.isVirtual() && "Cannot harden a physical register!");

auto *RC = MRI->getRegClass(Reg);
int Bytes = TRI->getRegSizeInBits(*RC) / 8;
Expand Down
31 changes: 31 additions & 0 deletions llvm/test/CodeGen/X86/speculative-load-hardening.ll
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Expand Up @@ -1161,3 +1161,34 @@ define void @idempotent_atomic(ptr %x) speculative_load_hardening {
%tmp = atomicrmw or ptr %x, i32 0 seq_cst
ret void
}

; Make sure we don't crash on longjmps (PR60081).
declare void @llvm.eh.sjlj.longjmp(ptr)
define void @test_longjmp(ptr %env) speculative_load_hardening {
; X64-LABEL: test_longjmp:
; X64: # %bb.0:
; X64-NEXT: pushq %rbp
; X64-NEXT: .cfi_def_cfa_offset 16
; X64-NEXT: .cfi_offset %rbp, -16
; X64-NEXT: movq %rsp, %rax
; X64-NEXT: movq $-1, %rcx
; X64-NEXT: sarq $63, %rax
; X64-NEXT: orq %rax, %rdi
; X64-NEXT: movq (%rdi), %rbp
; X64-NEXT: movq 8(%rdi), %rcx
; X64-NEXT: movq 16(%rdi), %rsp
; X64-NEXT: orq %rax, %rcx
; X64-NEXT: jmpq *%rcx
;
; X64-LFENCE-LABEL: test_longjmp:
; X64-LFENCE: # %bb.0:
; X64-LFENCE-NEXT: pushq %rbp
; X64-LFENCE-NEXT: .cfi_def_cfa_offset 16
; X64-LFENCE-NEXT: .cfi_offset %rbp, -16
; X64-LFENCE-NEXT: movq (%rdi), %rbp
; X64-LFENCE-NEXT: movq 8(%rdi), %rax
; X64-LFENCE-NEXT: movq 16(%rdi), %rsp
; X64-LFENCE-NEXT: jmpq *%rax
call void @llvm.eh.sjlj.longjmp(ptr %env)
unreachable
}