Extract run_rpc_server to libbinder_common
We have two very similar uses of RunRpcServerCallback; extract them to
a common place, using a closure to encapsulate the specific behavior
for notifiying readiness.
This also neatly encapsulates all the unsafe code, and justification
of it, in one place.
Bug: 187444679
Test: atest ComposTestCase
Change-Id: If23f862748b2f921690820eaa6ee80e4b2829274
diff --git a/binder_common/rpc_server.rs b/binder_common/rpc_server.rs
new file mode 100644
index 0000000..36075cf
--- /dev/null
+++ b/binder_common/rpc_server.rs
@@ -0,0 +1,81 @@
+/*
+ * 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.
+ */
+
+//! Helpers for implementing an RPC Binder server.
+
+use binder::public_api::SpIBinder;
+use binder::unstable_api::AsNative;
+use std::os::raw;
+
+/// Run a binder RPC server, serving the supplied binder service implementation on the given vsock
+/// port.
+/// If and when the server is ready for connections (it is listening on the port) on_ready
+/// is called to allow appropriate action to be taken - e.g. to notify clients they
+/// may now attempt to connect.
+/// The current thread is joined to the binder thread pool to handle incoming messages.
+/// Returns true if the server has shutdown normally, false if it failed in some way.
+pub fn run_rpc_server<F>(service: SpIBinder, port: u32, on_ready: F) -> bool
+where
+ F: FnOnce(),
+{
+ let mut ready_notifier = ReadyNotifier(Some(on_ready));
+ ready_notifier.run_server(service, port)
+}
+
+struct ReadyNotifier<F>(Option<F>)
+where
+ F: FnOnce();
+
+impl<F> ReadyNotifier<F>
+where
+ F: FnOnce(),
+{
+ fn run_server(&mut self, mut service: SpIBinder, port: u32) -> bool {
+ let service = service.as_native_mut() as *mut binder_rpc_unstable_bindgen::AIBinder;
+ let param = self.as_void_ptr();
+
+ // SAFETY: Service ownership is transferring to the server and won't be valid afterward.
+ // Plus the binder objects are threadsafe.
+ // RunRpcServerCallback does not retain a reference to ready_callback, and only ever
+ // calls it with the param we provide during the lifetime of self.
+ unsafe {
+ binder_rpc_unstable_bindgen::RunRpcServerCallback(
+ service,
+ port,
+ Some(Self::ready_callback),
+ param,
+ )
+ }
+ }
+
+ fn as_void_ptr(&mut self) -> *mut raw::c_void {
+ self as *mut _ as *mut raw::c_void
+ }
+
+ unsafe extern "C" fn ready_callback(param: *mut raw::c_void) {
+ // SAFETY: This is only ever called by RunRpcServerCallback, within the lifetime of the
+ // ReadyNotifier, with param taking the value returned by as_void_ptr (so a properly aligned
+ // non-null pointer to an initialized instance).
+ let ready_notifier = param as *mut Self;
+ ready_notifier.as_mut().unwrap().notify()
+ }
+
+ fn notify(&mut self) {
+ if let Some(on_ready) = self.0.take() {
+ on_ready();
+ }
+ }
+}