[cfi] Fix missing !type annotation.

[eugenis]

Summary

CFI (only in the cross-dso mode) fails to set !type annotations when
a function is used before it is defined.

[pcc]

lib/CodeGen/CodeGenModule.cpp

934

It looks like we can get here with declarations that are not of type FunctionDecl (mostly via SetInternalFunctionAttributes -- see http://llvm-cs.pcc.me.uk/tools/clang/lib/CodeGen/CodeGenModule.cpp/rSetInternalFunctionAttributes). I suppose that either means you would need to tolerate null pointers in CreateFunctionTypeMetadata or add an isa check here.

Please also add a test for one of those cases.

[pcc]

LGTM

[eugenis]

thanks!
r285650

lib/CodeGen/CodeGenModule.cpp

void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
   // Some C++ ABIs require 2-byte alignment for member functions, in order to
   // reserve a bit for differentiating between virtual and non-virtual member
   // functions. If the current target's C++ ABI requires this and this is a
   // member function, set its alignment accordingly.
   if (getTarget().getCXXABI().areMemberFunctionsAligned()) {
     if (F->getAlignment() < 2 && isa<CXXMethodDecl>(D))
       F->setAlignment(2);
   }
+
+  // In the cross-dso CFI mode, we want !type attributes on definitions only.
+  if (CodeGenOpts.SanitizeCfiCrossDso)
+    if (auto *FD = dyn_cast<FunctionDecl>(D))
+      CreateFunctionTypeMetadata(FD, F);
 }
 
 void CodeGenModule::SetCommonAttributes(const Decl *D,
                                         llvm::GlobalValue *GV) {
   if (const auto *ND = dyn_cast_or_null<NamedDecl>(D))
     setGlobalVisibility(GV, ND);
   else
     GV->setVisibility(llvm::GlobalValue::DefaultVisibility);
if (!LangOpts.Sanitize.has(SanitizerKind::CFIICall))
     return;
 
   // Non-static class methods are handled via vtable pointer checks elsewhere.
   if (isa<CXXMethodDecl>(FD) && !cast<CXXMethodDecl>(FD)->isStatic())
     return;
 
   // Additionally, if building with cross-DSO support...
   if (CodeGenOpts.SanitizeCfiCrossDso) {
-    // Don't emit entries for function declarations. In cross-DSO mode these are
-    // handled with better precision at run time.
-    if (!FD->hasBody())
-      return;
     // Skip available_externally functions. They won't be codegen'ed in the
     // current module anyway.
     if (getContext().GetGVALinkageForFunction(FD) == GVA_AvailableExternally)
       return;
   }
 
   llvm::Metadata *MD = CreateMetadataIdentifierForType(FD->getType());
   F->addTypeMetadata(0, MD);
void CodeGenModule::SetFunctionAttributes(GlobalDecl GD, llvm::Function *F,
   }
 
   if (isa<CXXConstructorDecl>(FD) || isa<CXXDestructorDecl>(FD))
     F->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
   else if (const auto *MD = dyn_cast<CXXMethodDecl>(FD))
     if (MD->isVirtual())
       F->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
 
+  // Don't emit entries for function declarations in the cross-DSO mode. This
+  // is handled with better precision by the receiving DSO.
+  if (!CodeGenOpts.SanitizeCfiCrossDso)
     CreateFunctionTypeMetadata(FD, F);
 }
 
 void CodeGenModule::addUsedGlobal(llvm::GlobalValue *GV) {
   assert(!GV->isDeclaration() &&
          "Only globals with definition can force usage.");
   LLVMUsed.emplace_back(GV);
 }
 

test/CodeGen/cfi-icall-cross-dso2.c

+// RUN: %clang_cc1 -triple x86_64-unknown-linux -O1 -fblocks \
+// RUN:   -fsanitize=cfi-icall -fsanitize-cfi-cross-dso \
+// RUN:   -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: define void @f() {{.*}} !type !{{.*}} !type !{{.*}}
+void f(void);
+void (*pf)(void) = f;
+void f(void) { }
+
+// Check that we do not crash on non-FunctionDecl definitions.
+void (^g)(void) = ^{};