From 42c17ec5ac8cadf351ec63234124ab40d59feaab Mon Sep 17 00:00:00 2001 From: Vedant Kumar Date: Tue, 14 Mar 2017 01:56:34 +0000 Subject: [ubsan] Add a nullability sanitizer Teach UBSan to detect when a value with the _Nonnull type annotation assumes a null value. Call expressions, initializers, assignments, and return statements are all checked. Because _Nonnull does not affect IRGen, the new checks are disabled by default. The new driver flags are: -fsanitize=nullability-arg (_Nonnull violation in call) -fsanitize=nullability-assign (_Nonnull violation in assignment) -fsanitize=nullability-return (_Nonnull violation in return stmt) -fsanitize=nullability (all of the above) This patch builds on top of UBSan's existing support for detecting violations of the nonnull attributes ('nonnull' and 'returns_nonnull'), and relies on the compiler-rt support for those checks. Eventually we will need to update the diagnostic messages in compiler-rt (there are FIXME's for this, which will be addressed in a follow-up). One point of note is that the nullability-return check is only allowed to kick in if all arguments to the function satisfy their nullability preconditions. This makes it necessary to emit some null checks in the function body itself. Testing: check-clang and check-ubsan. I also built some Apple ObjC frameworks with an asserts-enabled compiler, and verified that we get valid reports. Differential Revision: https://reviews.llvm.org/D30762 llvm-svn: 297700 --- clang/lib/CodeGen/CodeGenFunction.cpp | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'clang/lib/CodeGen/CodeGenFunction.cpp') diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp index 5f793f8..11660b4 100644 --- a/clang/lib/CodeGen/CodeGenFunction.cpp +++ b/clang/lib/CodeGen/CodeGenFunction.cpp @@ -822,6 +822,18 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, } } + // If we're checking nullability, we need to know whether we can check the + // return value. Initialize the flag to 'true' and refine it in EmitParmDecl. + if (SanOpts.has(SanitizerKind::NullabilityReturn)) { + auto Nullability = FnRetTy->getNullability(getContext()); + if (Nullability && *Nullability == NullabilityKind::NonNull) { + if (!(SanOpts.has(SanitizerKind::ReturnsNonnullAttribute) && + CurCodeDecl && CurCodeDecl->getAttr())) + RetValNullabilityPrecondition = + llvm::ConstantInt::getTrue(getLLVMContext()); + } + } + // If we're in C++ mode and the function name is "main", it is guaranteed // to be norecurse by the standard (3.6.1.3 "The function main shall not be // used within a program"). -- cgit v1.1