CFI: Fix methods as function pointer cast

Fix casting between methods and function pointers by assigning a
secondary type id to methods with their concrete self so they can be
used as function pointers.

Author: rcvalle

compiler/rustc_codegen_llvm/src/declare.rs

@@ -141,20 +141,30 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
 
         if self.tcx.sess.is_sanitizer_cfi_enabled() {
             if let Some(instance) = instance {
+                let mut typeids = Vec::new();
                 let typeid = typeid_for_instance(self.tcx, &instance, TypeIdOptions::empty());
+                typeids.push(typeid.clone());
                 self.set_type_metadata(llfn, typeid);
                 let typeid =
                     typeid_for_instance(self.tcx, &instance, TypeIdOptions::GENERALIZE_POINTERS);
+                typeids.push(typeid.clone());
                 self.add_type_metadata(llfn, typeid);
                 let typeid =
                     typeid_for_instance(self.tcx, &instance, TypeIdOptions::NORMALIZE_INTEGERS);
+                typeids.push(typeid.clone());
                 self.add_type_metadata(llfn, typeid);
                 let typeid = typeid_for_instance(
                     self.tcx,
                     &instance,
                     TypeIdOptions::GENERALIZE_POINTERS | TypeIdOptions::NORMALIZE_INTEGERS,
                 );
+                typeids.push(typeid.clone());
                 self.add_type_metadata(llfn, typeid);
+                let typeid =
+                    typeid_for_instance(self.tcx, &instance, TypeIdOptions::NO_TYPE_ERASURE);
+                if !typeids.contains(&typeid) {
+                    self.add_type_metadata(llfn, typeid);
+                }
             } else {
                 let typeid = typeid_for_fnabi(self.tcx, fn_abi, TypeIdOptions::empty());
                 self.set_type_metadata(llfn, typeid);

compiler/rustc_symbol_mangling/src/typeid.rs

@@ -16,6 +16,7 @@ bitflags! {
         const GENERALIZE_POINTERS = 1;
         const GENERALIZE_REPR_C = 2;
         const NORMALIZE_INTEGERS = 4;
+        const NO_TYPE_ERASURE = 8;
     }
 }
 

compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs

@@ -1045,28 +1045,34 @@ pub fn transform_fnabi<'tcx>(
                     && !fn_abi.args.is_empty()
                     && fn_abi.args[0].layout.ty.is_ref()
                 {
-                    // Replace the concrete self by a reference to a trait object (i.e., perform
-                    // type erasure).
-                    let self_ty = if fn_abi.args[0].layout.ty.is_mutable_ptr() {
-                        Ty::new_mut_ref(
-                            tcx,
-                            tcx.lifetimes.re_erased,
-                            new_dynamic_trait(
-                                tcx,
-                                trait_ref.skip_binder().def_id,
-                                trait_ref.skip_binder().args,
-                            ),
-                        )
+                    let self_ty = if options.contains(EncodeTyOptions::NO_TYPE_ERASURE) {
+                        // Do not perform type erasure for assigning a secondary type id to methods
+                        // with their concrete self so they can be used as function pointers.
+                        return fn_abi.clone();
                     } else {
-                        Ty::new_imm_ref(
-                            tcx,
-                            tcx.lifetimes.re_erased,
-                            new_dynamic_trait(
+                        // Replace the concrete self by a reference to a trait object (i.e., perform
+                        // type erasure).
+                        if fn_abi.args[0].layout.ty.is_mutable_ptr() {
+                            Ty::new_mut_ref(
                                 tcx,
-                                trait_ref.skip_binder().def_id,
-                                trait_ref.skip_binder().args,
-                            ),
-                        )
+                                tcx.lifetimes.re_erased,
+                                new_dynamic_trait(
+                                    tcx,
+                                    trait_ref.skip_binder().def_id,
+                                    trait_ref.skip_binder().args,
+                                ),
+                            )
+                        } else {
+                            Ty::new_imm_ref(
+                                tcx,
+                                tcx.lifetimes.re_erased,
+                                new_dynamic_trait(
+                                    tcx,
+                                    trait_ref.skip_binder().def_id,
+                                    trait_ref.skip_binder().args,
+                                ),
+                            )
+                        }
                     };
                     let mut fn_abi = fn_abi.clone();
                     // HACK(rcvalle): It is okay to not replace or update the entire ArgAbi here

tests/codegen/sanitizer/cfi/emit-type-metadata-id-itanium-cxx-abi-method-secondary-typeid.rs

@@ -0,0 +1,22 @@
+// Verifies that a secondary type metadata identifier is assigned to methods with their concrete
+// self so they can be used as function pointers.
+//
+//@ needs-sanitizer-cfi
+//@ compile-flags: -Clto -Cno-prepopulate-passes -Copt-level=0 -Zsanitizer=cfi -Ctarget-feature=-crt-static
+
+#![crate_type="lib"]
+
+trait Trait1 {
+    fn foo(&self);
+}
+
+struct Type1;
+
+impl Trait1 for Type1 {
+    fn foo(&self) {}
+    // CHECK: define{{.*}}3foo{{.*}}!type ![[TYPE1:[0-9]+]] !type !{{[0-9]+}} !type !{{[0-9]+}} !type !{{[0-9]+}} !type ![[TYPE2:[0-9]+]]
+}
+
+
+// CHECK: ![[TYPE1]] = !{i64 0, !"_ZTSFvu3refIu3dynIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}6Trait1u6regionEEE"}
+// CHECK: ![[TYPE2]] = !{i64 0, !"_ZTSFvu3refIu{{[0-9]+}}NtC{{[[:print:]]+}}_{{[[:print:]]+}}5Type1EE"}

tests/ui/sanitizer/cfi-method-fn-ptr-cast.rs

@@ -0,0 +1,21 @@
+// Verifies that casting a method to a function pointer works.
+//
+//@ needs-sanitizer-cfi
+//@ compile-flags: -Clto -Cprefer-dynamic=off -Ctarget-feature=-crt-static -Zsanitizer=cfi -Copt-level=0
+//@ run-pass
+
+trait Trait1 {
+    fn foo(&self);
+}
+
+struct Type1;
+
+impl Trait1 for Type1 {
+    fn foo(&self) {}
+}
+
+fn main() {
+    let type1 = Type1 {};
+    let f = <Type1 as Trait1>::foo;
+    f(&type1);
+}