[clang][UBSan] Sanitization for alignment assumptions.
Summary:
UB isn't nice. It's cool and powerful, but not nice.
Having a way to detect it is nice though.
[[ https://wg21.link/p1007r3 | P1007R3: std::assume_aligned ]] / http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1007r2.pdf says:
```
We propose to add this functionality via a library function instead of a core language attribute.
...
If the pointer passed in is not aligned to at least N bytes, calling assume_aligned results in undefined behaviour.
```
This differential teaches clang to sanitize all the various variants of this assume-aligned attribute.
Requires D54588 for LLVM IRBuilder changes.
The compiler-rt part is D54590.
This is a second commit, the original one was r351105,
which was mass-reverted in r351159 because 2 compiler-rt tests were failing.
Reviewers: ABataev, craig.topper, vsk, rsmith, rnk, #sanitizers, erichkeane, filcab, rjmccall
Reviewed By: rjmccall
Subscribers: chandlerc, ldionne, EricWF, mclow.lists, cfe-commits, bkramer
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D54589
llvm-svn: 351177
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 455a254..7d494bb 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2410,7 +2410,10 @@
if (!AVAttr)
if (const auto *TOTy = dyn_cast<TypedefType>(OTy))
AVAttr = TOTy->getDecl()->getAttr<AlignValueAttr>();
- if (AVAttr) {
+ if (AVAttr && !SanOpts.has(SanitizerKind::Alignment)) {
+ // If alignment-assumption sanitizer is enabled, we do *not* add
+ // alignment attribute here, but emit normal alignment assumption,
+ // so the UBSAN check could function.
llvm::Value *AlignmentValue =
EmitScalarExpr(AVAttr->getAlignment());
llvm::ConstantInt *AlignmentCI =
@@ -4535,13 +4538,14 @@
llvm::Value *Alignment = EmitScalarExpr(AA->getAlignment());
llvm::ConstantInt *AlignmentCI = cast<llvm::ConstantInt>(Alignment);
- EmitAlignmentAssumption(Ret.getScalarVal(), AlignmentCI->getZExtValue(),
- OffsetValue);
+ EmitAlignmentAssumption(Ret.getScalarVal(), RetTy, Loc, AA->getLocation(),
+ AlignmentCI->getZExtValue(), OffsetValue);
} else if (const auto *AA = TargetDecl->getAttr<AllocAlignAttr>()) {
- llvm::Value *ParamVal =
- CallArgs[AA->getParamIndex().getLLVMIndex()].getRValue(
- *this).getScalarVal();
- EmitAlignmentAssumption(Ret.getScalarVal(), ParamVal);
+ llvm::Value *AlignmentVal = CallArgs[AA->getParamIndex().getLLVMIndex()]
+ .getRValue(*this)
+ .getScalarVal();
+ EmitAlignmentAssumption(Ret.getScalarVal(), RetTy, Loc, AA->getLocation(),
+ AlignmentVal);
}
}