CFI: Rewrite closure and coroutine instances to their trait method

maurer · maurer · commit 63ca77cd6613 · 2024-03-29T17:56:39.000Z
Similar to methods on a trait object, the most common way to indirectly
call a closure or coroutine is through the vtable on the appropriate
trait. This uses the same approach as we use for trait methods, after
backing out the trait arguments from the type.
diff --git a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
@@ -10,6 +10,7 @@
 use rustc_data_structures::base_n;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
+use rustc_hir::lang_items::LangItem;
 use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{
@@ -1152,43 +1153,91 @@ pub fn typeid_for_instance<'tcx>(
         instance.args = tcx.mk_args_trait(self_ty, List::empty());
     } else if matches!(instance.def, ty::InstanceDef::Virtual(..)) {
         instance.args = strip_receiver_auto(tcx, instance.args);
+    } else if let ty::InstanceDef::VTableShim(def_id) = instance.def
+        && let Some(trait_id) = tcx.trait_of_item(def_id)
+    {
+        // VTableShims may have a trait method, but a concrete Self. This is not suitable for a vtable,
+        // as the caller will not know the concrete Self.
+        let trait_ref = ty::TraitRef::new(tcx, trait_id, instance.args);
+        let invoke_ty = trait_object_ty(tcx, ty::Binder::dummy(trait_ref));
+        instance.args = tcx.mk_args_trait(invoke_ty, trait_ref.args.into_iter().skip(1));
     }
 
-    if !options.contains(EncodeTyOptions::NO_SELF_TYPE_ERASURE)
-        && let Some(impl_id) = tcx.impl_of_method(instance.def_id())
-        && let Some(trait_ref) = tcx.impl_trait_ref(impl_id)
-    {
-        let impl_method = tcx.associated_item(instance.def_id());
-        let method_id = impl_method
-            .trait_item_def_id
-            .expect("Part of a trait implementation, but not linked to the def_id?");
-        let trait_method = tcx.associated_item(method_id);
-        let trait_id = trait_ref.skip_binder().def_id;
-        if traits::is_vtable_safe_method(tcx, trait_id, trait_method)
-            && tcx.object_safety_violations(trait_id).is_empty()
+    if !options.contains(EncodeTyOptions::NO_SELF_TYPE_ERASURE) {
+        if let Some(impl_id) = tcx.impl_of_method(instance.def_id())
+            && let Some(trait_ref) = tcx.impl_trait_ref(impl_id)
         {
-            // Trait methods will have a Self polymorphic parameter, where the concreteized
-            // implementatation will not. We need to walk back to the more general trait method
-            let trait_ref = tcx.instantiate_and_normalize_erasing_regions(
-                instance.args,
-                ty::ParamEnv::reveal_all(),
-                trait_ref,
-            );
+            let impl_method = tcx.associated_item(instance.def_id());
+            let method_id = impl_method
+                .trait_item_def_id
+                .expect("Part of a trait implementation, but not linked to the def_id?");
+            let trait_method = tcx.associated_item(method_id);
+            let trait_id = trait_ref.skip_binder().def_id;
+            if traits::is_vtable_safe_method(tcx, trait_id, trait_method)
+                && tcx.object_safety_violations(trait_id).is_empty()
+            {
+                // Trait methods will have a Self polymorphic parameter, where the concreteized
+                // implementatation will not. We need to walk back to the more general trait method
+                let trait_ref = tcx.instantiate_and_normalize_erasing_regions(
+                    instance.args,
+                    ty::ParamEnv::reveal_all(),
+                    trait_ref,
+                );
+                let invoke_ty = trait_object_ty(tcx, ty::Binder::dummy(trait_ref));
+
+                // At the call site, any call to this concrete function through a vtable will be
+                // `Virtual(method_id, idx)` with appropriate arguments for the method. Since we have the
+                // original method id, and we've recovered the trait arguments, we can make the callee
+                // instance we're computing the alias set for match the caller instance.
+                //
+                // Right now, our code ignores the vtable index everywhere, so we use 0 as a placeholder.
+                // If we ever *do* start encoding the vtable index, we will need to generate an alias set
+                // based on which vtables we are putting this method into, as there will be more than one
+                // index value when supertraits are involved.
+                instance.def = ty::InstanceDef::Virtual(method_id, 0);
+                let abstract_trait_args =
+                    tcx.mk_args_trait(invoke_ty, trait_ref.args.into_iter().skip(1));
+                instance.args = instance.args.rebase_onto(tcx, impl_id, abstract_trait_args);
+            }
+        } else if tcx.is_closure_like(instance.def_id()) {
+            // We're either a closure or a coroutine. Our goal is to find the trait we're defined on,
+            // instantiate it, and take the type of its only method as our own.
+            let closure_ty = instance.ty(tcx, ty::ParamEnv::reveal_all());
+            let (trait_id, inputs) = match closure_ty.kind() {
+                ty::Closure(..) => {
+                    let closure_args = instance.args.as_closure();
+                    let trait_id = tcx.fn_trait_kind_to_def_id(closure_args.kind()).unwrap();
+                    let tuple_args =
+                        tcx.instantiate_bound_regions_with_erased(closure_args.sig()).inputs()[0];
+                    (trait_id, tuple_args)
+                }
+                ty::Coroutine(..) => (
+                    tcx.require_lang_item(LangItem::Coroutine, None),
+                    instance.args.as_coroutine().resume_ty(),
+                ),
+                ty::CoroutineClosure(..) => (
+                    tcx.require_lang_item(LangItem::FnOnce, None),
+                    tcx.instantiate_bound_regions_with_erased(
+                        instance.args.as_coroutine_closure().coroutine_closure_sig(),
+                    )
+                    .tupled_inputs_ty,
+                ),
+                x => bug!("Unexpected type kind for closure-like: {x:?}"),
+            };
+            let trait_ref = ty::TraitRef::new(tcx, trait_id, [closure_ty, inputs]);
             let invoke_ty = trait_object_ty(tcx, ty::Binder::dummy(trait_ref));
+            let abstract_args = tcx.mk_args_trait(invoke_ty, trait_ref.args.into_iter().skip(1));
+            // There should be exactly one method on this trait, and it should be the one we're
+            // defining.
+            let call = tcx
+                .associated_items(trait_id)
+                .in_definition_order()
+                .find(|it| it.kind == ty::AssocKind::Fn)
+                .expect("No call-family function on closure-like Fn trait?")
+                .def_id;
 
-            // At the call site, any call to this concrete function through a vtable will be
-            // `Virtual(method_id, idx)` with appropriate arguments for the method. Since we have the
-            // original method id, and we've recovered the trait arguments, we can make the callee
-            // instance we're computing the alias set for match the caller instance.
-            //
-            // Right now, our code ignores the vtable index everywhere, so we use 0 as a placeholder.
-            // If we ever *do* start encoding the vtable index, we will need to generate an alias set
-            // based on which vtables we are putting this method into, as there will be more than one
-            // index value when supertraits are involved.
-            instance.def = ty::InstanceDef::Virtual(method_id, 0);
-            let abstract_trait_args =
-                tcx.mk_args_trait(invoke_ty, trait_ref.args.into_iter().skip(1));
-            instance.args = instance.args.rebase_onto(tcx, impl_id, abstract_trait_args);
+            instance.def = ty::InstanceDef::Virtual(call, 0);
+            instance.args = abstract_args;
         }
     }
 
diff --git a/tests/ui/sanitizer/cfi-async-closures.rs b/tests/ui/sanitizer/cfi-async-closures.rs
@@ -10,6 +10,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -Z panic-abort-tests -C prefer-dynamic=off
 //@ run-pass
 
 #![feature(async_closure)]
@@ -27,4 +28,6 @@ fn main() {
    let f = identity(async || ());
    let _ = f.async_call(());
    let _ = f();
+   let g: Box<dyn FnOnce() -> _> = Box::new(f) as _;
+   let _ = g();
 }
diff --git a/tests/ui/sanitizer/cfi-closure-fn-ptr-cast.rs b/tests/ui/sanitizer/cfi-closure-fn-ptr-cast.rs
diff --git a/tests/ui/sanitizer/cfi-closures.rs b/tests/ui/sanitizer/cfi-closures.rs
@@ -0,0 +1,83 @@
+// Check various forms of dynamic closure calls
+
+//@ revisions: cfi kcfi
+// FIXME(#122848) Remove only-linux once OSX CFI binaries work
+//@ only-linux
+//@ [cfi] needs-sanitizer-cfi
+//@ [kcfi] needs-sanitizer-kcfi
+//@ compile-flags: -C target-feature=-crt-static
+//@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
+//@ [cfi] compile-flags: -Z sanitizer=cfi
+//@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -Z panic-abort-tests -C prefer-dynamic=off
+//@ compile-flags: --test
+//@ run-pass
+
+#![feature(fn_traits)]
+#![feature(unboxed_closures)]
+#![feature(cfg_sanitize)]
+
+fn foo<'a, T>() -> Box<dyn Fn(&'a T) -> &'a T> {
+    Box::new(|x| x)
+}
+
+#[test]
+fn dyn_fn_with_params() {
+    let x = 3;
+    let f = foo();
+    f(&x);
+    // FIXME remove once drops are working.
+    std::mem::forget(f);
+}
+
+#[test]
+fn call_fn_trait() {
+   let f: &(dyn Fn()) = &(|| {}) as _;
+   f.call(());
+}
+
+#[test]
+fn fn_ptr_cast() {
+    let f: &fn() = &((|| ()) as _);
+    f();
+}
+
+fn use_fnmut<F: FnMut()>(mut f: F) {
+    f()
+}
+
+#[test]
+fn fn_to_fnmut() {
+    let f: &(dyn Fn()) = &(|| {}) as _;
+    use_fnmut(f);
+}
+
+fn hrtb_helper(f: &dyn for<'a> Fn(&'a usize)) {
+    f(&10)
+}
+
+#[test]
+fn hrtb_fn() {
+    hrtb_helper((&|x: &usize| println!("{}", *x)) as _)
+}
+
+#[test]
+fn fnonce() {
+    let f: Box<dyn FnOnce()> = Box::new(|| {}) as _;
+    f();
+}
+
+fn use_closure<C>(call: extern "rust-call" fn(&C, ()) -> i32, f: &C) -> i32 {
+    call(f, ())
+}
+
+#[test]
+// FIXME after KCFI reify support is added, remove this
+// It will appear to work if you test locally, set -C opt-level=0 to see it fail.
+#[cfg_attr(sanitize = "kcfi", ignore)]
+fn closure_addr_taken() {
+    let x = 3i32;
+    let f = || x;
+    let call = Fn::<()>::call;
+    use_closure(call, &f);
+}
diff --git a/tests/ui/sanitizer/cfi-coroutine.rs b/tests/ui/sanitizer/cfi-coroutine.rs
@@ -0,0 +1,29 @@
+// Verifies that we can call dynamic coroutines
+
+//@ revisions: cfi kcfi
+// FIXME(#122848) Remove only-linux once OSX CFI binaries work
+//@ only-linux
+//@ [cfi] needs-sanitizer-cfi
+//@ [kcfi] needs-sanitizer-kcfi
+//@ compile-flags: -C target-feature=-crt-static
+//@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
+//@ [cfi] compile-flags: -Z sanitizer=cfi
+//@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ compile-flags: --test
+//@ run-pass
+
+#![feature(coroutines)]
+#![feature(coroutine_trait)]
+
+use std::ops::{Coroutine, CoroutineState};
+use std::pin::{pin, Pin};
+
+fn main() {
+    let mut coro = |x: i32| {
+        yield x;
+        "done"
+    };
+    let mut abstract_coro: Pin<&mut dyn Coroutine<i32,Yield=i32,Return=&'static str>> = pin!(coro);
+    assert_eq!(abstract_coro.as_mut().resume(2), CoroutineState::Yielded(2));
+    assert_eq!(abstract_coro.as_mut().resume(0), CoroutineState::Complete("done"));
+}
