Merge "Add Accessor::from_binder" into main am: a222734

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/3362266

Change-Id: I692d08b3b2a320bdc9bb686008ea445e942105d8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

Author: Treehugger Robot

libs/binder/rust/src/system_only.rs

@@ -91,6 +91,32 @@ impl Accessor {
         Accessor { accessor }
     }
 
+    /// Creates a new Accessor instance based on an existing Accessor's binder.
+    /// This is useful when the Accessor instance is hosted in another process
+    /// that has the permissions to create the socket connection FD.
+    ///
+    /// The `instance` argument must match the instance that the original Accessor
+    /// is responsible for.
+    /// `instance` must not contain null bytes and is used to create a CString to
+    /// pass through FFI.
+    /// The `binder` argument must be a valid binder from an Accessor
+    pub fn from_binder(instance: &str, binder: SpIBinder) -> Option<Accessor> {
+        let inst = CString::new(instance).unwrap();
+
+        // Safety: All `SpIBinder` objects (the `binder` argument) hold a valid pointer
+        // to an `AIBinder` that is guaranteed to remain valid for the lifetime of the
+        // SpIBinder. `ABinderRpc_Accessor_fromBinder` creates a new pointer to that binder
+        // that it is responsible for.
+        // The `inst` argument is a new CString that will copied by
+        // `ABinderRpc_Accessor_fromBinder` and not modified.
+        let accessor =
+            unsafe { sys::ABinderRpc_Accessor_fromBinder(inst.as_ptr(), binder.as_raw()) };
+        if accessor.is_null() {
+            return None;
+        }
+        Some(Accessor { accessor })
+    }
+
     /// Get the underlying binder for this Accessor for when it needs to be either
     /// registered with service manager or sent to another process.
     pub fn as_binder(&self) -> Option<SpIBinder> {

libs/binder/rust/tests/integration.rs

@@ -1038,6 +1038,34 @@ mod tests {
         assert!(deleted.load(Ordering::Relaxed));
     }
 
+    #[test]
+    fn test_accessor_from_accessor_binder() {
+        let get_connection_info = move |_instance: &str| None;
+        let accessor = Accessor::new("foo.service", get_connection_info);
+        let accessor2 =
+            Accessor::from_binder("foo.service", accessor.as_binder().unwrap()).unwrap();
+        assert_eq!(accessor.as_binder(), accessor2.as_binder());
+    }
+
+    #[test]
+    fn test_accessor_from_non_accessor_binder() {
+        let service_name = "rust_test_ibinder";
+        let _process = ScopedServiceProcess::new(service_name);
+        let binder = binder::get_service(service_name).unwrap();
+        assert!(binder.is_binder_alive());
+
+        let accessor = Accessor::from_binder("rust_test_ibinder", binder);
+        assert!(accessor.is_none());
+    }
+
+    #[test]
+    fn test_accessor_from_wrong_accessor_binder() {
+        let get_connection_info = move |_instance: &str| None;
+        let accessor = Accessor::new("foo.service", get_connection_info);
+        let accessor2 = Accessor::from_binder("NOT.foo.service", accessor.as_binder().unwrap());
+        assert!(accessor2.is_none());
+    }
+
     #[tokio::test]
     async fn reassociate_rust_binder_async() {
         let service_name = "testing_service";