binder: add async Rust support

Test: add and run integration tests
Change-Id: I7671eeb7dfe4cc45efd57756753b361440529a3c

8 files changed, 353 insertions, 14 deletions

diff --git a/libs/binder/rust/Android.bp b/libs/binder/rust/Android.bp
index ecb044e589..d323022b01 100644
--- a/libs/binder/rust/Android.bp
+++ b/libs/binder/rust/Android.bp
@@ -33,6 +33,27 @@ rust_library {
 }
 
 rust_library {
+    name: "libbinder_tokio_rs",
+    crate_name: "binder_tokio",
+    srcs: ["binder_tokio/lib.rs"],
+    rustlibs: [
+        "libbinder_rs",
+        "libtokio",
+    ],
+    host_supported: true,
+    target: {
+        darwin: {
+            enabled: false,
+        }
+    },
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.compos",
+        "com.android.virt",
+    ],
+}
+
+rust_library {
     name: "libbinder_ndk_sys",
     crate_name: "binder_ndk_sys",
     srcs: [
diff --git a/libs/binder/rust/binder_tokio/lib.rs b/libs/binder/rust/binder_tokio/lib.rs
new file mode 100644
index 0000000000..a71ddda073
--- /dev/null
+++ b/libs/binder/rust/binder_tokio/lib.rs
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! This crate lets you use the Tokio `spawn_blocking` pool with AIDL in async
+//! Rust code.
+//!
+//! This crate works by defining a type [`Tokio`], which you can use as the
+//! generic parameter in the async version of the trait generated by the AIDL
+//! compiler.
+//! ```text
+//! use binder_tokio::Tokio;
+//!
+//! binder::get_interface::<dyn SomeAsyncInterface<Tokio>>("...").
+//! ```
+//!
+//! [`Tokio`]: crate::Tokio
+
+use binder::public_api::{BinderAsyncPool, BoxFuture};
+use binder::StatusCode;
+use std::future::Future;
+
+/// Use the Tokio `spawn_blocking` pool with AIDL.
+pub enum Tokio {}
+
+impl BinderAsyncPool for Tokio {
+    fn spawn<'a, F1, F2, Fut, A, B, E>(spawn_me: F1, after_spawn: F2) -> BoxFuture<'a, Result<B, E>>
+    where
+        F1: FnOnce() -> A,
+        F2: FnOnce(A) -> Fut,
+        Fut: Future<Output = Result<B, E>>,
+        F1: Send + 'static,
+        F2: Send + 'a,
+        Fut: Send + 'a,
+        A: Send + 'static,
+        B: Send + 'a,
+        E: From<crate::StatusCode>,
+    {
+        let handle = tokio::task::spawn_blocking(spawn_me);
+        Box::pin(async move {
+            // The `is_panic` branch is not actually reachable in Android as we compile
+            // with `panic = abort`.
+            match handle.await {
+                Ok(res) => after_spawn(res).await,
+                Err(e) if e.is_panic() => std::panic::resume_unwind(e.into_panic()),
+                Err(e) if e.is_cancelled() => Err(StatusCode::FAILED_TRANSACTION.into()),
+                Err(_) => Err(StatusCode::UNKNOWN_ERROR.into()),
+            }
+        })
+    }
+}
+
+
diff --git a/libs/binder/rust/src/binder.rs b/libs/binder/rust/src/binder.rs
index cc5dd06c9b..4e048d7c5a 100644
--- a/libs/binder/rust/src/binder.rs
+++ b/libs/binder/rust/src/binder.rs
@@ -713,12 +713,14 @@ macro_rules! declare_binder_interface {
         $interface:path[$descriptor:expr] {
             native: $native:ident($on_transact:path),
             proxy: $proxy:ident,
+            $(async: $async_interface:ident,)?
         }
     } => {
         $crate::declare_binder_interface! {
             $interface[$descriptor] {
                 native: $native($on_transact),
                 proxy: $proxy {},
+                $(async: $async_interface,)?
                 stability: $crate::Stability::default(),
             }
         }
@@ -728,6 +730,7 @@ macro_rules! declare_binder_interface {
         $interface:path[$descriptor:expr] {
             native: $native:ident($on_transact:path),
             proxy: $proxy:ident,
+            $(async: $async_interface:ident,)?
             stability: $stability:expr,
         }
     } => {
@@ -735,6 +738,7 @@ macro_rules! declare_binder_interface {
             $interface[$descriptor] {
                 native: $native($on_transact),
                 proxy: $proxy {},
+                $(async: $async_interface,)?
                 stability: $stability,
             }
         }
@@ -746,6 +750,7 @@ macro_rules! declare_binder_interface {
             proxy: $proxy:ident {
                 $($fname:ident: $fty:ty = $finit:expr),*
             },
+            $(async: $async_interface:ident,)?
         }
     } => {
         $crate::declare_binder_interface! {
@@ -754,6 +759,7 @@ macro_rules! declare_binder_interface {
                 proxy: $proxy {
                     $($fname: $fty = $finit),*
                 },
+                $(async: $async_interface,)?
                 stability: $crate::Stability::default(),
             }
         }
@@ -765,6 +771,7 @@ macro_rules! declare_binder_interface {
             proxy: $proxy:ident {
                 $($fname:ident: $fty:ty = $finit:expr),*
             },
+            $(async: $async_interface:ident,)?
             stability: $stability:expr,
         }
     } => {
@@ -776,6 +783,7 @@ macro_rules! declare_binder_interface {
                 proxy: $proxy {
                     $($fname: $fty = $finit),*
                 },
+                $(async: $async_interface,)?
                 stability: $stability,
             }
         }
@@ -791,6 +799,8 @@ macro_rules! declare_binder_interface {
                 $($fname:ident: $fty:ty = $finit:expr),*
             },
 
+            $( async: $async_interface:ident, )?
+
             stability: $stability:expr,
         }
     } => {
@@ -924,7 +934,7 @@ macro_rules! declare_binder_interface {
             }
         }
 
-        impl std::fmt::Debug for dyn $interface {
+        impl std::fmt::Debug for dyn $interface + '_ {
             fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                 f.pad(stringify!($interface))
             }
@@ -938,6 +948,73 @@ macro_rules! declare_binder_interface {
                     .expect(concat!("Error cloning interface ", stringify!($interface)))
             }
         }
+
+        $(
+        // Async interface trait implementations.
+        impl<P: $crate::BinderAsyncPool> $crate::FromIBinder for dyn $async_interface<P> {
+            fn try_from(mut ibinder: $crate::SpIBinder) -> $crate::Result<$crate::Strong<dyn $async_interface<P>>> {
+                use $crate::AssociateClass;
+
+                let existing_class = ibinder.get_class();
+                if let Some(class) = existing_class {
+                    if class != <$native as $crate::Remotable>::get_class() &&
+                        class.get_descriptor() == <$native as $crate::Remotable>::get_descriptor()
+                    {
+                        // The binder object's descriptor string matches what we
+                        // expect. We still need to treat this local or already
+                        // associated object as remote, because we can't cast it
+                        // into a Rust service object without a matching class
+                        // pointer.
+                        return Ok($crate::Strong::new(Box::new(<$proxy as $crate::Proxy>::from_binder(ibinder)?)));
+                    }
+                }
+
+                if ibinder.associate_class(<$native as $crate::Remotable>::get_class()) {
+                    let service: $crate::Result<$crate::Binder<$native>> =
+                        std::convert::TryFrom::try_from(ibinder.clone());
+                    if let Ok(service) = service {
+                        // We were able to associate with our expected class and
+                        // the service is local.
+                        todo!()
+                        //return Ok($crate::Strong::new(Box::new(service)));
+                    } else {
+                        // Service is remote
+                        return Ok($crate::Strong::new(Box::new(<$proxy as $crate::Proxy>::from_binder(ibinder)?)));
+                    }
+                }
+
+                Err($crate::StatusCode::BAD_TYPE.into())
+            }
+        }
+
+        impl<P: $crate::BinderAsyncPool> $crate::parcel::Serialize for dyn $async_interface<P> + '_ {
+            fn serialize(&self, parcel: &mut $crate::parcel::Parcel) -> $crate::Result<()> {
+                let binder = $crate::Interface::as_binder(self);
+                parcel.write(&binder)
+            }
+        }
+
+        impl<P: $crate::BinderAsyncPool> $crate::parcel::SerializeOption for dyn $async_interface<P> + '_ {
+            fn serialize_option(this: Option<&Self>, parcel: &mut $crate::parcel::Parcel) -> $crate::Result<()> {
+                parcel.write(&this.map($crate::Interface::as_binder))
+            }
+        }
+
+        impl<P: $crate::BinderAsyncPool> std::fmt::Debug for dyn $async_interface<P> + '_ {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                f.pad(stringify!($async_interface))
+            }
+        }
+
+        /// Convert a &dyn $async_interface to Strong<dyn $async_interface>
+        impl<P: $crate::BinderAsyncPool> std::borrow::ToOwned for dyn $async_interface<P> {
+            type Owned = $crate::Strong<dyn $async_interface<P>>;
+            fn to_owned(&self) -> Self::Owned {
+                self.as_binder().into_interface()
+                    .expect(concat!("Error cloning interface ", stringify!($async_interface)))
+            }
+        }
+        )?
     };
 }
 
diff --git a/libs/binder/rust/src/binder_async.rs b/libs/binder/rust/src/binder_async.rs
new file mode 100644
index 0000000000..214c0b5f26
--- /dev/null
+++ b/libs/binder/rust/src/binder_async.rs
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use std::future::Future;
+use std::pin::Pin;
+
+/// A type alias for a pinned, boxed future that lets you write shorter code without littering it
+/// with Pin and Send bounds.
+pub type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;
+
+/// A thread pool for running binder transactions.
+pub trait BinderAsyncPool {
+    /// This function should conceptually behave like this:
+    ///
+    /// ```text
+    /// let result = spawn_thread(|| spawn_me()).await;
+    /// return after_spawn(result).await;
+    /// ```
+    ///
+    /// If the spawning fails for some reason, the method may also skip the `after_spawn` closure
+    /// and immediately return an error.
+    ///
+    /// The only difference between different implementations should be which
+    /// `spawn_thread` method is used. For Tokio, it would be `tokio::task::spawn_blocking`.
+    ///
+    /// This method has the design it has because the only way to define a trait that
+    /// allows the return type of the spawn to be chosen by the caller is to return a
+    /// boxed `Future` trait object, and including `after_spawn` in the trait function
+    /// allows the caller to avoid double-boxing if they want to do anything to the value
+    /// returned from the spawned thread.
+    fn spawn<'a, F1, F2, Fut, A, B, E>(spawn_me: F1, after_spawn: F2) -> BoxFuture<'a, Result<B, E>>
+    where
+        F1: FnOnce() -> A,
+        F2: FnOnce(A) -> Fut,
+        Fut: Future<Output = Result<B, E>>,
+        F1: Send + 'static,
+        F2: Send + 'a,
+        Fut: Send + 'a,
+        A: Send + 'static,
+        B: Send + 'a,
+        E: From<crate::StatusCode>;
+}
diff --git a/libs/binder/rust/src/lib.rs b/libs/binder/rust/src/lib.rs
index 81b620e85f..2ac2d2f0bc 100644
--- a/libs/binder/rust/src/lib.rs
+++ b/libs/binder/rust/src/lib.rs
@@ -98,6 +98,7 @@ mod proxy;
 
 #[macro_use]
 mod binder;
+mod binder_async;
 mod error;
 mod native;
 mod state;
@@ -111,6 +112,7 @@ pub use crate::binder::{
     Stability, Strong, TransactionCode, TransactionFlags, Weak, FIRST_CALL_TRANSACTION,
     FLAG_CLEAR_BUF, FLAG_ONEWAY, FLAG_PRIVATE_LOCAL, LAST_CALL_TRANSACTION,
 };
+pub use crate::binder_async::{BoxFuture, BinderAsyncPool};
 pub use error::{status_t, ExceptionCode, Result, Status, StatusCode};
 pub use native::{add_service, force_lazy_services_persist, register_lazy_service, Binder};
 pub use parcel::{OwnedParcel, Parcel};
@@ -133,8 +135,9 @@ pub mod public_api {
         wait_for_interface,
     };
     pub use super::{
-        BinderFeatures, DeathRecipient, ExceptionCode, IBinder, Interface, ProcessState, SpIBinder,
-        Status, StatusCode, Strong, ThreadState, Weak, WpIBinder,
+        BinderAsyncPool, BinderFeatures, BoxFuture, DeathRecipient, ExceptionCode, IBinder,
+        Interface, ProcessState, SpIBinder, Status, StatusCode, Strong, ThreadState, Weak,
+        WpIBinder,
     };
 
     /// Binder result containing a [`Status`] on error.
diff --git a/libs/binder/rust/src/parcel.rs b/libs/binder/rust/src/parcel.rs
index 9dba950677..a0e147860d 100644
--- a/libs/binder/rust/src/parcel.rs
+++ b/libs/binder/rust/src/parcel.rs
@@ -83,6 +83,19 @@ impl OwnedParcel {
         Self { ptr }
     }
 
+    /// Convert the provided parcel to an owned parcel, or return `None` if it
+    /// is borrowed.
+    pub fn try_from(parcel: Parcel) -> Option<OwnedParcel> {
+        match &parcel {
+            Parcel::Owned(ptr) => {
+                let ptr = *ptr;
+                std::mem::forget(parcel);
+                Some(OwnedParcel { ptr })
+            }
+            Parcel::Borrowed(_) => None,
+        }
+    }
+
     /// Create an owned reference to a parcel object from a raw pointer.
     ///
     /// # Safety
diff --git a/libs/binder/rust/tests/Android.bp b/libs/binder/rust/tests/Android.bp
index ecc61f4683..2d1175be75 100644
--- a/libs/binder/rust/tests/Android.bp
+++ b/libs/binder/rust/tests/Android.bp
@@ -13,6 +13,8 @@ rust_test {
     rustlibs: [
         "libbinder_rs",
         "libselinux_bindgen",
+        "libbinder_tokio_rs",
+        "libtokio",
     ],
     shared_libs: [
         "libselinux",
diff --git a/libs/binder/rust/tests/integration.rs b/libs/binder/rust/tests/integration.rs
index 335e8d848f..3c2907393f 100644
--- a/libs/binder/rust/tests/integration.rs
+++ b/libs/binder/rust/tests/integration.rs
@@ -17,7 +17,7 @@
 //! Rust Binder crate integration tests
 
 use binder::declare_binder_interface;
-use binder::parcel::Parcel;
+use binder::parcel::{Parcel, OwnedParcel};
 use binder::{
     Binder, BinderFeatures, IBinderInternal, Interface, StatusCode, ThreadState, TransactionCode,
     FIRST_CALL_TRANSACTION,
@@ -154,12 +154,25 @@ pub trait ITest: Interface {
     fn get_selinux_context(&self) -> binder::Result<String>;
 }
 
+/// Async trivial testing binder interface
+pub trait IATest<P>: Interface {
+    /// Returns a test string
+    fn test(&self) -> binder::BoxFuture<'static, binder::Result<String>>;
+
+    /// Return the arguments sent via dump
+    fn get_dump_args(&self) -> binder::BoxFuture<'static, binder::Result<Vec<String>>>;
+
+    /// Returns the caller's SELinux context
+    fn get_selinux_context(&self) -> binder::BoxFuture<'static, binder::Result<String>>;
+}
+
 declare_binder_interface! {
     ITest["android.os.ITest"] {
         native: BnTest(on_transact),
         proxy: BpTest {
             x: i32 = 100
         },
+        async: IATest,
     }
 }
 
@@ -201,6 +214,32 @@ impl ITest for BpTest {
     }
 }
 
+impl<P: binder::BinderAsyncPool> IATest<P> for BpTest {
+    fn test(&self) -> binder::BoxFuture<'static, binder::Result<String>> {
+        let binder = self.binder.clone();
+        P::spawn(
+            move || binder.transact(TestTransactionCode::Test as TransactionCode, 0, |_| Ok(())).map(|p| OwnedParcel::try_from(p).unwrap()),
+            |reply| async move { reply?.into_parcel().read() }
+        )
+    }
+
+    fn get_dump_args(&self) -> binder::BoxFuture<'static, binder::Result<Vec<String>>> {
+        let binder = self.binder.clone();
+        P::spawn(
+            move || binder.transact(TestTransactionCode::GetDumpArgs as TransactionCode, 0, |_| Ok(())).map(|p| OwnedParcel::try_from(p).unwrap()),
+            |reply| async move { reply?.into_parcel().read() }
+        )
+    }
+
+    fn get_selinux_context(&self) -> binder::BoxFuture<'static, binder::Result<String>> {
+        let binder = self.binder.clone();
+        P::spawn(
+            move || binder.transact(TestTransactionCode::GetSelinuxContext as TransactionCode, 0, |_| Ok(())).map(|p| OwnedParcel::try_from(p).unwrap()),
+            |reply| async move { reply?.into_parcel().read() }
+        )
+    }
+}
+
 impl ITest for Binder<BnTest> {
     fn test(&self) -> binder::Result<String> {
         self.0.test()
@@ -215,6 +254,23 @@ impl ITest for Binder<BnTest> {
     }
 }
 
+impl<P: binder::BinderAsyncPool> IATest<P> for Binder<BnTest> {
+    fn test(&self) -> binder::BoxFuture<'static, binder::Result<String>> {
+        let res = self.0.test();
+        Box::pin(async move { res })
+    }
+
+    fn get_dump_args(&self) -> binder::BoxFuture<'static, binder::Result<Vec<String>>> {
+        let res = self.0.get_dump_args();
+        Box::pin(async move { res })
+    }
+
+    fn get_selinux_context(&self) -> binder::BoxFuture<'static, binder::Result<String>> {
+        let res = self.0.get_selinux_context();
+        Box::pin(async move { res })
+    }
+}
+
 /// Trivial testing binder interface
 pub trait ITestSameDescriptor: Interface {}
 
@@ -255,7 +311,9 @@ mod tests {
         SpIBinder, StatusCode, Strong,
     };
 
-    use super::{BnTest, ITest, ITestSameDescriptor, TestService, RUST_SERVICE_BINARY};
+    use binder_tokio::Tokio;
+
+    use super::{BnTest, ITest, IATest, ITestSameDescriptor, TestService, RUST_SERVICE_BINARY};
 
     pub struct ScopedServiceProcess(Child);
 
@@ -303,12 +361,20 @@ mod tests {
             binder::get_interface::<dyn ITest>("this_service_does_not_exist").err(),
             Some(StatusCode::NAME_NOT_FOUND)
         );
+        assert_eq!(
+            binder::get_interface::<dyn IATest<Tokio>>("this_service_does_not_exist").err(),
+            Some(StatusCode::NAME_NOT_FOUND)
+        );
 
         // The service manager service isn't an ITest, so this must fail.
         assert_eq!(
             binder::get_interface::<dyn ITest>("manager").err(),
             Some(StatusCode::BAD_TYPE)
         );
+        assert_eq!(
+            binder::get_interface::<dyn IATest<Tokio>>("manager").err(),
+            Some(StatusCode::BAD_TYPE)
+        );
     }
 
     #[test]
@@ -323,6 +389,10 @@ mod tests {
             binder::wait_for_interface::<dyn ITest>("manager").err(),
             Some(StatusCode::BAD_TYPE)
         );
+        assert_eq!(
+            binder::wait_for_interface::<dyn IATest<Tokio>>("manager").err(),
+            Some(StatusCode::BAD_TYPE)
+        );
     }
 
     #[test]
@@ -334,6 +404,15 @@ mod tests {
         assert_eq!(test_client.test().unwrap(), "trivial_client_test");
     }
 
+    #[tokio::test]
+    async fn trivial_client_async() {
+        let service_name = "trivial_client_test";
+        let _process = ScopedServiceProcess::new(service_name);
+        let test_client: Strong<dyn IATest<Tokio>> =
+            binder::get_interface(service_name).expect("Did not get manager binder service");
+        assert_eq!(test_client.test().await.unwrap(), "trivial_client_test");
+    }
+
     #[test]
     fn wait_for_trivial_client() {
         let service_name = "wait_for_trivial_client_test";
@@ -343,23 +422,47 @@ mod tests {
         assert_eq!(test_client.test().unwrap(), "wait_for_trivial_client_test");
     }
 
+    #[tokio::test]
+    async fn wait_for_trivial_client_async() {
+        let service_name = "wait_for_trivial_client_test";
+        let _process = ScopedServiceProcess::new(service_name);
+        let test_client: Strong<dyn IATest<Tokio>> =
+            binder::wait_for_interface(service_name).expect("Did not get manager binder service");
+        assert_eq!(test_client.test().await.unwrap(), "wait_for_trivial_client_test");
+    }
+
+    fn get_expected_selinux_context() -> &'static str {
+        unsafe {
+            let mut out_ptr = ptr::null_mut();
+            assert_eq!(selinux_sys::getcon(&mut out_ptr), 0);
+            assert!(!out_ptr.is_null());
+            CStr::from_ptr(out_ptr)
+                .to_str()
+                .expect("context was invalid UTF-8")
+        }
+    }
+
     #[test]
     fn get_selinux_context() {
         let service_name = "get_selinux_context";
         let _process = ScopedServiceProcess::new(service_name);
         let test_client: Strong<dyn ITest> =
             binder::get_interface(service_name).expect("Did not get manager binder service");
-        let expected_context = unsafe {
-            let mut out_ptr = ptr::null_mut();
-            assert_eq!(selinux_sys::getcon(&mut out_ptr), 0);
-            assert!(!out_ptr.is_null());
-            CStr::from_ptr(out_ptr)
-        };
         assert_eq!(
             test_client.get_selinux_context().unwrap(),
-            expected_context
-                .to_str()
-                .expect("context was invalid UTF-8"),
+            get_expected_selinux_context()
+        );
+    }
+
+    #[tokio::test]
+    async fn get_selinux_context_async() {
+        let service_name = "get_selinux_context";
+        let _process = ScopedServiceProcess::new(service_name);
+        let test_client: Strong<dyn IATest<Tokio>> =
+            binder::get_interface(service_name).expect("Did not get manager binder service");
+        assert_eq!(
+            test_client.get_selinux_context().await.unwrap(),
+            get_expected_selinux_context()
         );
     }