[ubsan] Don't emit function signatures for non-static member functions

The function sanitizer only checks indirect calls through function
pointers. This excludes all non-static member functions (constructor
calls, calls through thunks, etc. all use a separate code path). Don't
emit function signatures for functions that won't be checked.

Apart from cutting down on code size, this should fix a regression on
Linux caused by r313096. For context, see the mailing list discussion:

r313096 - [ubsan] Function Sanitizer: Don't require writable text segments

Testing: check-clang, check-ubsan

Differential Revision: https://reviews.llvm.org/D38913

llvm-svn: 315786

1 files changed, 10 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 26df45f5350..aac603c104d 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -789,6 +789,15 @@ static bool matchesStlAllocatorFn(const Decl *D, const ASTContext &Ctx) {
   return true;
 }
 
+/// Return the UBSan prologue signature for \p FD if one is available.
+static llvm::Constant *getPrologueSignature(CodeGenModule &CGM,
+                                            const FunctionDecl *FD) {
+  if (const auto *MD = dyn_cast<CXXMethodDecl>(FD))
+    if (!MD->isStatic())
+      return nullptr;
+  return CGM.getTargetCodeGenInfo().getUBSanFunctionSignature(CGM);
+}
+
 void CodeGenFunction::StartFunction(GlobalDecl GD,
                                     QualType RetTy,
                                     llvm::Function *Fn,
@@ -908,8 +917,7 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
   // prologue data.
   if (getLangOpts().CPlusPlus && SanOpts.has(SanitizerKind::Function)) {
     if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) {
-      if (llvm::Constant *PrologueSig =
-              CGM.getTargetCodeGenInfo().getUBSanFunctionSignature(CGM)) {
+      if (llvm::Constant *PrologueSig = getPrologueSignature(CGM, FD)) {
         llvm::Constant *FTRTTIConst =
             CGM.GetAddrOfRTTIDescriptor(FD->getType(), /*ForEH=*/true);
         llvm::Constant *FTRTTIConstEncoded =