Mark CXX module initializer with PACBTI attributes (#133716)

The CXX module initializer function, which is called at program startup,
needs to be tagged with Pointer Authentication and Branch Target
Identification marks whenever relevant.

Before this patch, in CPUs set up for PACBTI execution, the function
wasn't protected with return address signing and no BTI instruction was
inserted at the start of it, thus leading to an execution fault.

This patch fixes the issue by marking the function with the function
attributes related to PAC and BTI if relevant.

3 files changed, 17 insertions, 12 deletions

diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index 303d21e..8a214da 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -448,6 +448,11 @@ llvm::Function *CodeGenModule::CreateGlobalInitOrCleanUpFunction(
 
   if (Linkage == llvm::GlobalVariable::InternalLinkage)
     SetInternalFunctionAttributes(GlobalDecl(), Fn, FI);
+  else {
+    SetLLVMFunctionAttributes(GlobalDecl(), FI, Fn, false);
+    SetLLVMFunctionAttributesForDefinition(nullptr, Fn);
+    getTargetCodeGenInfo().setTargetAttributes(nullptr, Fn, *this);
+  }
 
   Fn->setCallingConv(getRuntimeCC());
 
diff --git a/clang/lib/CodeGen/Targets/AArch64.cpp b/clang/lib/CodeGen/Targets/AArch64.cpp
index 77e225d..f098f09e 100644
--- a/clang/lib/CodeGen/Targets/AArch64.cpp
+++ b/clang/lib/CodeGen/Targets/AArch64.cpp
@@ -136,13 +136,15 @@ public:
 
   void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
                            CodeGen::CodeGenModule &CGM) const override {
-    const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D);
-    if (!FD)
+    auto *Fn = dyn_cast<llvm::Function>(GV);
+    if (!Fn)
       return;
 
+    const auto *FD = dyn_cast_or_null<FunctionDecl>(D);
     TargetInfo::BranchProtectionInfo BPI(CGM.getLangOpts());
 
-    if (const auto *TA = FD->getAttr<TargetAttr>()) {
+    if (FD && FD->hasAttr<TargetAttr>()) {
+      const auto *TA = FD->getAttr<TargetAttr>();
       ParsedTargetAttr Attr =
           CGM.getTarget().parseTargetAttr(TA->getFeaturesStr());
       if (!Attr.BranchProtection.empty()) {
@@ -152,7 +154,6 @@ public:
         assert(Error.empty());
       }
     }
-    auto *Fn = cast<llvm::Function>(GV);
     setBranchProtectionFnAttributes(BPI, *Fn);
   }
 
diff --git a/clang/lib/CodeGen/Targets/ARM.cpp b/clang/lib/CodeGen/Targets/ARM.cpp
index dddf51a..68f9e01 100644
--- a/clang/lib/CodeGen/Targets/ARM.cpp
+++ b/clang/lib/CodeGen/Targets/ARM.cpp
@@ -134,14 +134,13 @@ public:
 
   void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
                            CodeGen::CodeGenModule &CGM) const override {
-    if (GV->isDeclaration())
+    auto *Fn = dyn_cast<llvm::Function>(GV);
+    if (!Fn)
       return;
-    const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D);
-    if (!FD)
-      return;
-    auto *Fn = cast<llvm::Function>(GV);
+    const auto *FD = dyn_cast_or_null<FunctionDecl>(D);
 
-    if (const auto *TA = FD->getAttr<TargetAttr>()) {
+    if (FD && FD->hasAttr<TargetAttr>()) {
+      const auto *TA = FD->getAttr<TargetAttr>();
       ParsedTargetAttr Attr =
           CGM.getTarget().parseTargetAttr(TA->getFeaturesStr());
       if (!Attr.BranchProtection.empty()) {
@@ -174,10 +173,10 @@ public:
       setBranchProtectionFnAttributes(BPI, (*Fn));
     }
 
-    const ARMInterruptAttr *Attr = FD->getAttr<ARMInterruptAttr>();
-    if (!Attr)
+    if (!FD || !FD->hasAttr<ARMInterruptAttr>())
       return;
 
+    const ARMInterruptAttr *Attr = FD->getAttr<ARMInterruptAttr>();
     const char *Kind;
     switch (Attr->getInterrupt()) {
     case ARMInterruptAttr::Generic: Kind = ""; break;