Add support for __declspec(guard(nocf))
Summary:
Avoid using the `nocf_check` attribute with Control Flow Guard. Instead, use a
new `"guard_nocf"` function attribute to indicate that checks should not be
added on indirect calls within that function. Add support for
`__declspec(guard(nocf))` following the same syntax as MSVC.
Reviewers: rnk, dmajor, pcc, hans, aaron.ballman
Reviewed By: aaron.ballman
Subscribers: aaron.ballman, tomrittervg, hiraditya, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D72167
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index b49b194..e4803fd 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -4415,6 +4415,17 @@
if (callOrInvoke)
*callOrInvoke = CI;
+ // If this is within a function that has the guard(nocf) attribute and is an
+ // indirect call, add the "guard_nocf" attribute to this call to indicate that
+ // Control Flow Guard checks should not be added, even if the call is inlined.
+ if (const auto *FD = dyn_cast_or_null<FunctionDecl>(CurFuncDecl)) {
+ if (const auto *A = FD->getAttr<CFGuardAttr>()) {
+ if (A->getGuard() == CFGuardAttr::GuardArg::nocf && !CI->getCalledFunction())
+ Attrs = Attrs.addAttribute(
+ getLLVMContext(), llvm::AttributeList::FunctionIndex, "guard_nocf");
+ }
+ }
+
// Apply the attributes and calling convention.
CI->setAttributes(Attrs);
CI->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));