Keystore 2.0: Enforce MAX_BOOT_LEVEL in software

Test: Initialize keystore.boot_level in init.rc; then
      adb setprop keystore.boot_level 40 and check logs
Test: Test program creates key with MAX_BOOT_LEVEL tag; ensure
      it can be used before bumping keystore.boot_level but not after
Bug: 176450483
Change-Id: I94ea178e0fd524bf0a5d65b016559ddd7766205f
diff --git a/keystore2/system_property/Android.bp b/keystore2/system_property/Android.bp
new file mode 100644
index 0000000..f6a810b
--- /dev/null
+++ b/keystore2/system_property/Android.bp
@@ -0,0 +1,43 @@
+// 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.
+
+rust_bindgen {
+    name: "libkeystore2_system_property_bindgen",
+    wrapper_src: "system_property_bindgen.hpp",
+    crate_name: "keystore2_system_property_bindgen",
+    source_stem: "bindings",
+
+    bindgen_flags: [
+        "--size_t-is-usize",
+        "--whitelist-function=__system_property_find",
+        "--whitelist-function=__system_property_read_callback",
+        "--whitelist-function=__system_property_wait",
+    ],
+}
+
+rust_library {
+    name: "libkeystore2_system_property-rust",
+    crate_name: "keystore2_system_property",
+    srcs: [
+        "lib.rs",
+    ],
+    rustlibs: [
+        "libanyhow",
+        "libkeystore2_system_property_bindgen",
+        "libthiserror",
+    ],
+    shared_libs: [
+        "libbase",
+    ],
+}