Ravenwood support for `SystemProperties`.

One of our final missing pieces of foundational functionality is
the SystemProperties key/value store.  Over the years, this key/value
store has been (ab)used to configure very obscure parts of the OS.

As tempting as it might be to simply let code rely on default return
values when a key is undefined, we'd like to ensure that code owners
carefully confirm any assumed behaviors.  To accomplish this, we
default to blocking both read/write access to keys until their use
has been explicitly audited.

Based on our guiding principles, as code owners support their APIs
under Ravenwood, they're expected to bring along all relevant tests,
which will uncover SystemProperties usage that needs triage, reducing
the risk of downstream clients uncovering that usage.

Tests can explicitly allow read/write access to specific properties
via their RavenwoodRule.Builder definition, which is also how we
ensure that all values are consistently reset between tests.

Bug: 319647875
Test: atest FrameworksCoreSystemPropertiesTestsRavenwood
Test: atest FrameworksCoreTestsRavenwood CtsOsTestCasesRavenwood
Change-Id: I6510e06c33ee8b2bf31b58f35faa07127ecd16b7

2 files changed, 211 insertions, 0 deletions

diff --git a/ravenwood/junit-src/android/platform/test/ravenwood/RavenwoodRule.java b/ravenwood/junit-src/android/platform/test/ravenwood/RavenwoodRule.java
index 53da8ba14a2c..dd442f08321f 100644
--- a/ravenwood/junit-src/android/platform/test/ravenwood/RavenwoodRule.java
+++ b/ravenwood/junit-src/android/platform/test/ravenwood/RavenwoodRule.java
@@ -62,6 +62,8 @@ public class RavenwoodRule implements TestRule {
 
     boolean mProvideMainThread = false;
 
+    final RavenwoodSystemProperties mSystemProperties = new RavenwoodSystemProperties();
+
     public RavenwoodRule() {
     }
 
@@ -98,6 +100,40 @@ public class RavenwoodRule implements TestRule {
             return this;
         }
 
+        /**
+         * Configure the given system property as immutable for the duration of the test.
+         * Read access to the key is allowed, and write access will fail. When {@code value} is
+         * {@code null}, the value is left as undefined.
+         *
+         * All properties in the {@code debug.*} namespace are automatically mutable, with no
+         * developer action required.
+         *
+         * Has no effect under non-Ravenwood environments.
+         */
+        public Builder setSystemPropertyImmutable(/* @NonNull */ String key,
+                /* @Nullable */ Object value) {
+            mRule.mSystemProperties.setValue(key, value);
+            mRule.mSystemProperties.setAccessReadOnly(key);
+            return this;
+        }
+
+        /**
+         * Configure the given system property as mutable for the duration of the test.
+         * Both read and write access to the key is allowed, and its value will be reset between
+         * each test. When {@code value} is {@code null}, the value is left as undefined.
+         *
+         * All properties in the {@code debug.*} namespace are automatically mutable, with no
+         * developer action required.
+         *
+         * Has no effect under non-Ravenwood environments.
+         */
+        public Builder setSystemPropertyMutable(/* @NonNull */ String key,
+                /* @Nullable */ Object value) {
+            mRule.mSystemProperties.setValue(key, value);
+            mRule.mSystemProperties.setAccessReadWrite(key);
+            return this;
+        }
+
         public RavenwoodRule build() {
             return mRule;
         }
diff --git a/ravenwood/junit-src/android/platform/test/ravenwood/RavenwoodSystemProperties.java b/ravenwood/junit-src/android/platform/test/ravenwood/RavenwoodSystemProperties.java
new file mode 100644
index 000000000000..85ad4e444f24
--- /dev/null
+++ b/ravenwood/junit-src/android/platform/test/ravenwood/RavenwoodSystemProperties.java
@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2024 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.
+ */
+
+package android.platform.test.ravenwood;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Predicate;
+
+class RavenwoodSystemProperties {
+    private final Map<String, String> mValues = new HashMap<>();
+
+    /** Set of additional keys that should be considered readable */
+    private final Set<String> mKeyReadable = new HashSet<>();
+    private final Predicate<String> mKeyReadablePredicate = (key) -> {
+        final String root = getKeyRoot(key);
+
+        if (root.startsWith("debug.")) return true;
+
+        // This set is carefully curated to help identify situations where a test may
+        // accidentally depend on a default value of an obscure property whose owner hasn't
+        // decided how Ravenwood should behave.
+        if (root.startsWith("boot.")) return true;
+        if (root.startsWith("build.")) return true;
+        if (root.startsWith("product.")) return true;
+        if (root.startsWith("soc.")) return true;
+        if (root.startsWith("system.")) return true;
+
+        switch (key) {
+            case "gsm.version.baseband":
+            case "no.such.thing":
+            case "ro.bootloader":
+            case "ro.debuggable":
+            case "ro.hardware":
+            case "ro.hw_timeout_multiplier":
+            case "ro.odm.build.media_performance_class":
+            case "ro.treble.enabled":
+            case "ro.vndk.version":
+                return true;
+        }
+
+        return mKeyReadable.contains(key);
+    };
+
+    /** Set of additional keys that should be considered writable */
+    private final Set<String> mKeyWritable = new HashSet<>();
+    private final Predicate<String> mKeyWritablePredicate = (key) -> {
+        final String root = getKeyRoot(key);
+
+        if (root.startsWith("debug.")) return true;
+
+        return mKeyWritable.contains(key);
+    };
+
+    public RavenwoodSystemProperties() {
+        // TODO: load these values from build.prop generated files
+        setValueForPartitions("product.brand", "Android");
+        setValueForPartitions("product.device", "Ravenwood");
+        setValueForPartitions("product.manufacturer", "Android");
+        setValueForPartitions("product.model", "Ravenwood");
+        setValueForPartitions("product.name", "Ravenwood");
+
+        setValueForPartitions("product.cpu.abilist", "x86_64");
+        setValueForPartitions("product.cpu.abilist32", "");
+        setValueForPartitions("product.cpu.abilist64", "x86_64");
+
+        setValueForPartitions("build.date", "Thu Jan 01 00:00:00 GMT 2024");
+        setValueForPartitions("build.date.utc", "1704092400");
+        setValueForPartitions("build.id", "MAIN");
+        setValueForPartitions("build.tags", "dev-keys");
+        setValueForPartitions("build.type", "userdebug");
+        setValueForPartitions("build.version.all_codenames", "REL");
+        setValueForPartitions("build.version.codename", "REL");
+        setValueForPartitions("build.version.incremental", "userdebug.ravenwood.20240101");
+        setValueForPartitions("build.version.known_codenames", "REL");
+        setValueForPartitions("build.version.release", "14");
+        setValueForPartitions("build.version.release_or_codename", "VanillaIceCream");
+        setValueForPartitions("build.version.sdk", "34");
+
+        setValue("ro.board.first_api_level", "1");
+        setValue("ro.product.first_api_level", "1");
+
+        setValue("ro.soc.manufacturer", "Android");
+        setValue("ro.soc.model", "Ravenwood");
+
+        setValue("ro.debuggable", "1");
+    }
+
+    Map<String, String> getValues() {
+        return new HashMap<>(mValues);
+    }
+
+    Predicate<String> getKeyReadablePredicate() {
+        return mKeyReadablePredicate;
+    }
+
+    Predicate<String> getKeyWritablePredicate() {
+        return mKeyWritablePredicate;
+    }
+
+    private static final String[] PARTITIONS = {
+            "bootimage",
+            "odm",
+            "product",
+            "system",
+            "system_ext",
+            "vendor",
+            "vendor_dlkm",
+    };
+
+    /**
+     * Set the given property for all possible partitions where it could be defined. For
+     * example, the value of {@code ro.build.type} is typically also mirrored under
+     * {@code ro.system.build.type}, etc.
+     */
+    private void setValueForPartitions(String key, String value) {
+        setValue("ro." + key, value);
+        for (String partition : PARTITIONS) {
+            setValue("ro." + partition + "." + key, value);
+        }
+    }
+
+    public void setValue(String key, Object value) {
+        final String valueString = (value == null) ? null : String.valueOf(value);
+        if ((valueString == null) || valueString.isEmpty()) {
+            mValues.remove(key);
+        } else {
+            mValues.put(key, valueString);
+        }
+    }
+
+    public void setAccessNone(String key) {
+        mKeyReadable.remove(key);
+        mKeyWritable.remove(key);
+    }
+
+    public void setAccessReadOnly(String key) {
+        mKeyReadable.add(key);
+        mKeyWritable.remove(key);
+    }
+
+    public void setAccessReadWrite(String key) {
+        mKeyReadable.add(key);
+        mKeyWritable.add(key);
+    }
+
+    /**
+     * Return the "root" of the given property key, stripping away any modifier prefix such as
+     * {@code ro.} or {@code persist.}.
+     */
+    private static String getKeyRoot(String key) {
+        if (key.startsWith("ro.")) {
+            return key.substring(3);
+        } else if (key.startsWith("persist.")) {
+            return key.substring(8);
+        } else {
+            return key;
+        }
+    }
+}