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/payload_config.rs b/microdroid_manager/src/payload_config.rs
new file mode 100644
index 0000000..1dd6d92
--- /dev/null
+++ b/microdroid_manager/src/payload_config.rs
@@ -0,0 +1,41 @@
+// 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.
+
+//! VM Payload Config
+
+use log::info;
+use serde::{Deserialize, Serialize};
+use std::fs::File;
+use std::io;
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub struct VmPayloadConfig {
+    #[serde(default)]
+    pub task: Option<Task>,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub struct Task {
+    pub command: String,
+    #[serde(default)]
+    pub args: Vec<String>,
+}
+
+impl VmPayloadConfig {
+    pub fn load_from(path: &str) -> io::Result<VmPayloadConfig> {
+        info!("loading config from {}...", path);
+        let file = File::open(path)?;
+        Ok(serde_json::from_reader(file)?)
+    }
+}