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[DebugInfo] Exclude memory location values as parameter entry values

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Abandon describing of loaded values due to safety concerns. Loaded
values are described as derefed memory location at caller point.
At callee we can unintentionally change that memory location which
would lead to different entry being printed value before and after
the memory location clobbering. This problem is described in
llvm.org/PR43343.

Patch by Nikola Prica

Differential Revision: https://reviews.llvm.org/D67717

llvm-svn: 373089
This commit is contained in:
Djordje Todorovic 2019-09-27 13:52:43 +00:00
parent 8a234db13c
commit 7c429fc379
3 changed files with 7 additions and 18 deletions
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7
lib/CodeGen/AsmPrinter/DwarfExpression.cpp
View File

@ -246,8 +246,8 @@ bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
// a call site parameter expression and if that expression is just a register
// location, emit it with addBReg and offset 0, because we should emit a DWARF
// expression representing a value, rather than a location.
if (!isMemoryLocation() && !HasComplexExpression && (!isParameterValue() ||
isEntryValue())) {
if (!isMemoryLocation() && !HasComplexExpression &&
(!isParameterValue() || isEntryValue())) {
for (auto &Reg : DwarfRegs) {
if (Reg.DwarfRegNo >= 0)
addReg(Reg.DwarfRegNo, Reg.Comment);
@ -413,6 +413,9 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
break;
case dwarf::DW_OP_deref:
assert(!isRegisterLocation());
// For more detailed explanation see llvm.org/PR43343.
assert(!isParameterValue() && "Parameter entry values should not be "
"dereferenced due to safety reasons.");
if (!isMemoryLocation() && ::isMemoryLocation(ExprCursor))
// Turning this into a memory location description makes the deref
// implicit.

12
lib/CodeGen/TargetInstrInfo.cpp
View File

@ -1133,18 +1133,6 @@ TargetInstrInfo::describeLoadedValue(const MachineInstr &MI) const {
} else if (MI.isMoveImmediate()) {
Op = &MI.getOperand(1);
return ParamLoadedValue(*Op, Expr);
} else if (MI.hasOneMemOperand()) {
int64_t Offset;
const auto &TRI = MF->getSubtarget().getRegisterInfo();
const auto &TII = MF->getSubtarget().getInstrInfo();
const MachineOperand *BaseOp;
if (!TII->getMemOperandWithOffset(MI, BaseOp, Offset, TRI))
return None;
Expr = DIExpression::prepend(Expr, DIExpression::DerefAfter, Offset);
Op = BaseOp;
return ParamLoadedValue(*Op, Expr);
}
return None;

6
test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir
View File

@ -21,10 +21,8 @@
# CHECK-NEXT: DW_AT_low_pc
# CHECK-EMPTY:
# CHECK-NEXT: DW_TAG_GNU_call_site_parameter
# CHECK-NEXT: DW_AT_location (DW_OP_reg2 RCX)
# CHECK-NEXT: DW_AT_GNU_call_site_value (DW_OP_fbreg +8, DW_OP_deref)
# CHECK-EMPTY:
# CHECK-NEXT: DW_TAG_GNU_call_site_parameter
# RCX loads memory location. We can't rely that memory location won't be changed.
# CHECK-NOT: DW_AT_location (DW_OP_reg2 RCX)
# CHECK-NEXT: DW_AT_location (DW_OP_reg4 RSI)
# CHECK-NEXT: DW_AT_GNU_call_site_value (DW_OP_lit4)
# CHECK-EMPTY: