From bcd35a8ec11ea000d6a6fc31becc549eb5c25a30 Mon Sep 17 00:00:00 2001 From: Anna Zaks Date: Fri, 11 Nov 2016 23:22:44 +0000 Subject: [tsan][clang] Introduce a function attribute to disable TSan checking at run time This introduces a function annotation that disables TSan checking for the function at run time. The benefit over attribute((no_sanitize("thread"))) is that the accesses within the callees will also be suppressed. The motivation for this attribute is a guarantee given by the objective C language that the calls to the reference count decrement and object deallocation will be synchronized. To model this properly, we would need to intercept all ref count decrement calls (which are very common in ObjC due to use of ARC) and also every single message send. Instead, we propose to just ignore all accesses made from within dealloc at run time. The main downside is that this still does not introduce any synchronization, which means we might still report false positives if the code that relies on this synchronization is not executed from within dealloc. However, we have not seen this in practice so far and think these cases will be very rare. (This problem is similar in nature to https://reviews.llvm.org/D21609; unfortunately, the same solution does not apply here.) Differential Revision: https://reviews.llvm.org/D25857 llvm-svn: 286672 --- clang/lib/CodeGen/CodeGenFunction.cpp | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'clang/lib/CodeGen/CodeGenFunction.cpp') diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp index aac8f0af860..b2243bcea1e 100644 --- a/clang/lib/CodeGen/CodeGenFunction.cpp +++ b/clang/lib/CodeGen/CodeGenFunction.cpp @@ -731,6 +731,20 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, if (SanOpts.has(SanitizerKind::SafeStack)) Fn->addFnAttr(llvm::Attribute::SafeStack); + // Ignore TSan memory acesses from within ObjC/ObjC++ dealloc, initialize, + // .cxx_destruct and all of their calees at run time. + if (SanOpts.has(SanitizerKind::Thread)) { + if (const auto *OMD = dyn_cast_or_null(D)) { + IdentifierInfo *II = OMD->getSelector().getIdentifierInfoForSlot(0); + if (OMD->getMethodFamily() == OMF_dealloc || + OMD->getMethodFamily() == OMF_initialize || + (OMD->getSelector().isUnarySelector() && II->isStr(".cxx_destruct"))) { + Fn->addFnAttr("sanitize_thread_no_checking_at_run_time"); + Fn->removeFnAttr(llvm::Attribute::SanitizeThread); + } + } + } + // Apply xray attributes to the function (as a string, for now) if (D && ShouldXRayInstrumentFunction()) { if (const auto *XRayAttr = D->getAttr()) { -- cgit v1.2.3