[clang] Sign function pointers passed to atexit and __cxa_atexit.

Author: ahmedbougacha

clang/lib/CodeGen/CGDeclCXX.cpp

@@ -232,7 +232,7 @@ void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
 
 /// Create a stub function, suitable for being passed to atexit,
 /// which passes the given address to the given destructor function.
-llvm::Function *CodeGenFunction::createAtExitStub(const VarDecl &VD,
+llvm::Constant *CodeGenFunction::createAtExitStub(const VarDecl &VD,
                                                   llvm::FunctionCallee dtor,
                                                   llvm::Constant *addr) {
   // Get the destructor function type, void(*)(void).
@@ -264,7 +264,12 @@ llvm::Function *CodeGenFunction::createAtExitStub(const VarDecl &VD,
 
   CGF.FinishFunction();
 
-  return fn;
+  // Get a proper function pointer.
+  FunctionProtoType::ExtProtoInfo EPI(getContext().getDefaultCallingConvention(
+      /*IsVariadic=*/false, /*IsCXXMethod=*/false));
+  QualType fnType = getContext().getFunctionType(getContext().VoidTy,
+                                                 {getContext().VoidPtrTy}, EPI);
+  return CGM.getFunctionPointer(fn, fnType);
 }
 
 /// Create a stub function, suitable for being passed to __pt_atexit_np,

clang/lib/CodeGen/CodeGenFunction.h

@@ -4685,7 +4685,7 @@ class CodeGenFunction : public CodeGenTypeCache {
   void EmitCXXGlobalVarDeclInit(const VarDecl &D, llvm::GlobalVariable *GV,
                                 bool PerformInit);
 
-  llvm::Function *createAtExitStub(const VarDecl &VD, llvm::FunctionCallee Dtor,
+  llvm::Constant *createAtExitStub(const VarDecl &VD, llvm::FunctionCallee Dtor,
                                    llvm::Constant *Addr);
 
   llvm::Function *createTLSAtExitStub(const VarDecl &VD,

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -2845,14 +2845,22 @@ static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
   if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit.getCallee()))
     fn->setDoesNotThrow();
 
+  auto &Context = CGF.CGM.getContext();
+  FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
+      /*IsVariadic=*/false, /*IsCXXMethod=*/false));
+  QualType fnType =
+      Context.getFunctionType(Context.VoidTy, {Context.VoidPtrTy}, EPI);
+  llvm::Constant *dtorCallee = cast<llvm::Constant>(dtor.getCallee());
+  dtorCallee = CGF.CGM.getFunctionPointer(dtorCallee, fnType);
+
   if (!addr)
     // addr is null when we are trying to register a dtor annotated with
     // __attribute__((destructor)) in a constructor function. Using null here is
     // okay because this argument is just passed back to the destructor
     // function.
     addr = llvm::Constant::getNullValue(CGF.Int8PtrTy);
 
-  llvm::Value *args[] = {dtor.getCallee(), addr, handle};
+  llvm::Value *args[] = {dtorCallee, addr, handle};
   CGF.EmitNounwindRuntimeCall(atexit, args);
 }
 

clang/test/CodeGenCXX/ptrauth-static-destructors.cpp

@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple arm64-apple-ios -fptrauth-calls -emit-llvm -std=c++11 %s -o - \
+// RUN:  | FileCheck %s --check-prefix=CXAATEXIT
+
+// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple arm64-apple-ios -fptrauth-calls -emit-llvm -std=c++11 %s -o - \
+// RUN:    -fno-use-cxa-atexit \
+// RUN:  | FileCheck %s --check-prefix=ATEXIT
+
+class Foo {
+ public:
+  ~Foo() {
+  }
+};
+
+Foo global;
+
+// CXAATEXIT: @_ZN3FooD1Ev.ptrauth = private constant { ptr, i32, i64, i64 } { ptr @_ZN3FooD1Ev, i32 0, i64 0, i64 10942 }, section "llvm.ptrauth", align 8
+// CXAATEXIT: define internal void @__cxx_global_var_init()
+// CXAATEXIT:   call i32 @__cxa_atexit(ptr @_ZN3FooD1Ev.ptrauth, ptr @global, ptr @__dso_handle)
+
+
+// ATEXIT: @__dtor_global.ptrauth = private constant { ptr, i32, i64, i64 } { ptr @__dtor_global, i32 0, i64 0, i64 10942 }, section "llvm.ptrauth", align 8
+// ATEXIT: define internal void @__cxx_global_var_init()
+// ATEXIT:   %{{.*}} = call i32 @atexit(ptr @__dtor_global.ptrauth)
+
+// ATEXIT: define internal void @__dtor_global() {{.*}} section "__TEXT,__StaticInit,regular,pure_instructions" {
+// ATEXIT:   %{{.*}} = call ptr @_ZN3FooD1Ev(ptr @global)