microdroid_manager: initial impl

It is started by init in microdroid and executes a command specified in
a VM payload config.

Bug: 189301496
Test: MicrodroidHostTestCases
  (in a microdroid, run /system/bin/microdroid_manager manulally)
Change-Id: I85c7e370d4a0dcf58b4aafbe6e9fba73e69c2a44
diff --git a/microdroid_manager/src/main.rs b/microdroid_manager/src/main.rs
new file mode 100644
index 0000000..4f87a40
--- /dev/null
+++ b/microdroid_manager/src/main.rs
@@ -0,0 +1,51 @@
+// Copyright 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.
+
+//! Microdroid Manager
+
+mod payload_config;
+mod signature;
+
+use android_logger::Config;
+use log::{info, Level};
+use payload_config::{Task, VmPayloadConfig};
+use std::io;
+use std::process::Command;
+
+const LOG_TAG: &str = "MicrodroidManager";
+
+fn main() -> io::Result<()> {
+    android_logger::init_once(Config::default().with_tag(LOG_TAG).with_min_level(Level::Debug));
+
+    info!("started.");
+
+    let signature = signature::load()?;
+    if !signature.payload_config_path.is_empty() {
+        let config = VmPayloadConfig::load_from(&signature.payload_config_path)?;
+        if let Some(main_task) = &config.task {
+            exec(main_task)?;
+        }
+    }
+
+    Ok(())
+}
+
+/// executes a task
+/// TODO(jooyung): fork a child process
+fn exec(task: &Task) -> io::Result<()> {
+    info!("executing main task {} {:?}...", task.command, task.args);
+    let exit_status = Command::new(&task.command).args(&task.args).status()?;
+    info!("exit with {}", &exit_status);
+    Ok(())
+}