1 files changed, 98 insertions, 3 deletions

diff --git a/core/java/com/android/internal/content/om/OverlayConfigParser.java b/core/java/com/android/internal/content/om/OverlayConfigParser.java
index faaf7d5cef18..8132652ed6f4 100644
--- a/core/java/com/android/internal/content/om/OverlayConfigParser.java
+++ b/core/java/com/android/internal/content/om/OverlayConfigParser.java
@@ -24,6 +24,8 @@ import android.content.pm.PackagePartitions;
 import android.content.pm.PackagePartitions.SystemPartition;
 import android.os.Build;
 import android.os.FileUtils;
+import android.os.SystemProperties;
+import android.text.TextUtils;
 import android.util.ArraySet;
 import android.util.Log;
 import android.util.Xml;
@@ -241,6 +243,18 @@ public final class OverlayConfigParser {
         }
     }
 
+    @FunctionalInterface
+    public interface SysPropWrapper{
+        /**
+         * Get system property
+         *
+         * @param property the key to look up.
+         *
+         * @return The property value if found, empty string otherwise.
+         */
+        String get(String property);
+    }
+
     /**
      * Retrieves overlays configured within the partition in increasing priority order.
      *
@@ -320,6 +334,76 @@ public final class OverlayConfigParser {
     }
 
     /**
+     * Expand the property inside a rro configuration path.
+     *
+     * A RRO configuration can contain a property, this method expands
+     * the property to its value.
+     *
+     * Only read only properties allowed, prefixed with ro. Other
+     * properties will raise exception.
+     *
+     * Only a single property in the path is allowed.
+     *
+     * Example "${ro.boot.hardware.sku}/config.xml" would expand to
+     *     "G020N/config.xml"
+     *
+     * @param configPath path to expand
+     * @param sysPropWrapper method used for reading properties
+     *
+     * @return The expanded path. Returns null if configPath is null.
+     */
+    @VisibleForTesting
+    public static String expandProperty(String configPath,
+            SysPropWrapper sysPropWrapper) {
+        if (configPath == null) {
+            return null;
+        }
+
+        int propStartPos = configPath.indexOf("${");
+        if (propStartPos == -1) {
+            // No properties inside the string, return as is
+            return configPath;
+        }
+
+        final StringBuilder sb = new StringBuilder();
+        sb.append(configPath.substring(0, propStartPos));
+
+        // Read out the end position
+        int propEndPos = configPath.indexOf("}", propStartPos);
+        if (propEndPos == -1) {
+            throw new IllegalStateException("Malformed property, unmatched braces, in: "
+                    + configPath);
+        }
+
+        // Confirm that there is only one property inside the string
+        if (configPath.indexOf("${", propStartPos + 2) != -1) {
+            throw new IllegalStateException("Only a single property supported in path: "
+                    + configPath);
+        }
+
+        final String propertyName = configPath.substring(propStartPos + 2, propEndPos);
+        if (!propertyName.startsWith("ro.")) {
+            throw new IllegalStateException("Only read only properties can be used when "
+                    + "merging RRO config files: " + propertyName);
+        }
+        final String propertyValue = sysPropWrapper.get(propertyName);
+        if (TextUtils.isEmpty(propertyValue)) {
+            throw new IllegalStateException("Property is empty or doesn't exist: " + propertyName);
+        }
+        Log.d(TAG, String.format("Using property in overlay config path: \"%s\"", propertyName));
+        sb.append(propertyValue);
+
+        // propEndPos points to '}', need to step to next character, might be outside of string
+        propEndPos = propEndPos + 1;
+        // Append the remainder, if exists
+        if (propEndPos < configPath.length()) {
+            sb.append(configPath.substring(propEndPos));
+        }
+
+        return sb.toString();
+    }
+
+    /**
      * Parses a <merge> tag within an overlay configuration file.
      *
      * Merge tags allow for other configuration files to be "merged" at the current parsing
@@ -331,10 +415,21 @@ public final class OverlayConfigParser {
             @Nullable OverlayScanner scanner,
             @Nullable Map<String, ParsedOverlayInfo> packageManagerOverlayInfos,
             @NonNull ParsingContext parsingContext) {
-        final String path = parser.getAttributeValue(null, "path");
+        final String path;
+
+        try {
+            SysPropWrapper sysPropWrapper = p -> {
+                return SystemProperties.get(p, "");
+            };
+            path = expandProperty(parser.getAttributeValue(null, "path"), sysPropWrapper);
+        } catch (IllegalStateException e) {
+            throw new IllegalStateException(String.format("<merge> path expand error in %s at %s",
+                    configFile, parser.getPositionDescription()), e);
+        }
+
         if (path == null) {
-            throw new IllegalStateException(String.format("<merge> without path in %s at %s"
-                    + configFile, parser.getPositionDescription()));
+            throw new IllegalStateException(String.format("<merge> without path in %s at %s",
+                    configFile, parser.getPositionDescription()));
         }
 
         if (path.startsWith("/")) {