From bd1c0870198e025f92d31eead0fb2019c4057a4a Mon Sep 17 00:00:00 2001 From: Roman Lebedev Date: Tue, 15 Jan 2019 09:44:25 +0000 Subject: [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 --- clang/lib/CodeGen/CGCall.cpp | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) (limited to 'clang/lib/CodeGen/CGCall.cpp') diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index 455a25434ff..7d494bb1f1c 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -2410,7 +2410,10 @@ void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI, if (!AVAttr) if (const auto *TOTy = dyn_cast(OTy)) AVAttr = TOTy->getDecl()->getAttr(); - 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 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo, llvm::Value *Alignment = EmitScalarExpr(AA->getAlignment()); llvm::ConstantInt *AlignmentCI = cast(Alignment); - EmitAlignmentAssumption(Ret.getScalarVal(), AlignmentCI->getZExtValue(), - OffsetValue); + EmitAlignmentAssumption(Ret.getScalarVal(), RetTy, Loc, AA->getLocation(), + AlignmentCI->getZExtValue(), OffsetValue); } else if (const auto *AA = TargetDecl->getAttr()) { - 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); } } -- cgit v1.2.3