[PATCH] D38913: [ubsan] Don't emit function signatures for virtual methods

[Vedant Kumar via Phabricator via cfe-commits]

vsk created this revision.

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

Supersedes https://reviews.llvm.org/D38903.


https://reviews.llvm.org/D38913

Files:
  lib/CodeGen/CodeGenFunction.cpp
  test/CodeGenCXX/catch-undef-behavior.cpp


Index: test/CodeGenCXX/catch-undef-behavior.cpp
===================================================================
--- test/CodeGenCXX/catch-undef-behavior.cpp
+++ test/CodeGenCXX/catch-undef-behavior.cpp
@@ -426,6 +426,66 @@
   p(42);
 }
 
+namespace FunctionSanitizerVirtualCalls {
+struct A {
+  virtual void f() {}
+  virtual void g() {}
+  void h() {}
+};
+
+struct B : virtual A {
+  virtual void b() {}
+  virtual void f();
+  void g() final {}
+  static void q() {}
+};
+
+void B::f() {}
+
+void force_irgen() {
+  A a;
+  a.g();
+  a.h();
+
+  B b;
+  b.f();
+  b.b();
+  b.g();
+  B::q();
+}
+
+// CHECK-LABEL: define void @_ZN29FunctionSanitizerVirtualCalls1B1fEv
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define void @_ZTv0_n24_N29FunctionSanitizerVirtualCalls1B1fEv
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define void @_ZN29FunctionSanitizerVirtualCalls11force_irgenEv()
+// CHECK: prologue
+//
+// CHECK-LABEL: define linkonce_odr void @_ZN29FunctionSanitizerVirtualCalls1AC1Ev
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define linkonce_odr void @_ZN29FunctionSanitizerVirtualCalls1A1gEv
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define linkonce_odr void @_ZN29FunctionSanitizerVirtualCalls1A1hEv
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define linkonce_odr void @_ZN29FunctionSanitizerVirtualCalls1BC1Ev
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define linkonce_odr void @_ZN29FunctionSanitizerVirtualCalls1B1bEv
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define linkonce_odr void @_ZN29FunctionSanitizerVirtualCalls1B1gEv
+// CHECK-NOT: prologue
+//
+// CHECK-LABEL: define linkonce_odr void @_ZN29FunctionSanitizerVirtualCalls1B1qEv
+// CHECK: prologue
+
+}
+
 namespace UpcastPointerTest {
 struct S {};
 struct T : S { double d; };
Index: lib/CodeGen/CodeGenFunction.cpp
===================================================================
--- lib/CodeGen/CodeGenFunction.cpp
+++ lib/CodeGen/CodeGenFunction.cpp
@@ -789,6 +789,15 @@
   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 @@
   // 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 =

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