From 7a368968648cb2faec42c9f41c062ef8177a075f Mon Sep 17 00:00:00 2001 From: Reid Kleckner Date: Thu, 6 Sep 2018 18:25:39 +0000 Subject: [PATCH] Re-land r334417 "[MS] Use mangled names and comdats for string merging with ASan" The issue with -fprofile-generate was fixed and the dependent CL relanded in r340232. llvm-svn: 341572 --- clang/lib/CodeGen/CodeGenModule.cpp | 12 +++++------- clang/test/CodeGen/asan-strings.c | 17 +++++++++++++++++ 2 files changed, 22 insertions(+), 7 deletions(-) create mode 100644 clang/test/CodeGen/asan-strings.c diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index 51869ef..5fec6c7 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -4305,15 +4305,13 @@ CodeGenModule::GetAddrOfConstantStringFromLiteral(const StringLiteral *S, StringRef GlobalVariableName; llvm::GlobalValue::LinkageTypes LT; - // Mangle the string literal if the ABI allows for it. However, we cannot - // do this if we are compiling with ASan or -fwritable-strings because they - // rely on strings having normal linkage. - if (!LangOpts.WritableStrings && - !LangOpts.Sanitize.has(SanitizerKind::Address) && - getCXXABI().getMangleContext().shouldMangleStringLiteral(S)) { + // Mangle the string literal if that's how the ABI merges duplicate strings. + // Don't do it if they are writable, since we don't want writes in one TU to + // affect strings in another. + if (getCXXABI().getMangleContext().shouldMangleStringLiteral(S) && + !LangOpts.WritableStrings) { llvm::raw_svector_ostream Out(MangledNameBuffer); getCXXABI().getMangleContext().mangleStringLiteral(S, Out); - LT = llvm::GlobalValue::LinkOnceODRLinkage; GlobalVariableName = MangledNameBuffer; } else { diff --git a/clang/test/CodeGen/asan-strings.c b/clang/test/CodeGen/asan-strings.c new file mode 100644 index 0000000..fc9c31b --- /dev/null +++ b/clang/test/CodeGen/asan-strings.c @@ -0,0 +1,17 @@ +// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=address -disable-llvm-passes -emit-llvm -o - %s | FileCheck %s --check-prefix=LINUX +// RUN: %clang_cc1 -triple x86_64-windows-msvc -fsanitize=address -disable-llvm-passes -emit-llvm -o - %s | FileCheck %s --check-prefix=WINDOWS +// RUN: %clang_cc1 -triple x86_64-windows-msvc -fsanitize=address -fwritable-strings -disable-llvm-passes -emit-llvm -o - %s | FileCheck %s --check-prefix=WINWRITE + +// On Linux (and basically every non-MS target) string literals are emitted with +// private linkage, which means ASan can freely instrument them. On Windows, +// they are emitted with comdats. ASan's global instrumentation code for COFF +// knows how to make the metadata comdat associative, so the string literal +// global is only registered if the instrumented global prevails during linking. + +const char *foo() { return "asdf"; } + +// LINUX: @.str = private unnamed_addr constant [5 x i8] c"asdf\00", align 1 + +// WINDOWS: @"??_C@_04JIHMPGLA@asdf?$AA@" = linkonce_odr dso_local unnamed_addr constant [5 x i8] c"asdf\00", comdat, align 1 + +// WINWRITE: @.str = private unnamed_addr global [5 x i8] c"asdf\00", align 1 -- 2.7.4