Initialize the appcompat system property folder

Certain applications may have their system properties overlaid with the
contents overlaid for appcompat purposes. Init must initialize the
appcompat folder, same as it does the standard folder.

Bug: 291814949
Test: manual
Change-Id: I6d239e0a10a1c81a05d4121e5fc2c41da5b3dbc4
Merged-In: I0c6a0f66dc543c6e861bc86a417e4feb5ecd7789
diff --git a/init/property_service.cpp b/init/property_service.cpp
index cdd0afe..21502fb 100644
--- a/init/property_service.cpp
+++ b/init/property_service.cpp
@@ -76,6 +76,10 @@
 #include "system/core/init/property_service.pb.h"
 #include "util.h"
 
+static constexpr char APPCOMPAT_OVERRIDE_PROP_FOLDERNAME[] =
+        "/dev/__properties__/appcompat_override";
+static constexpr char APPCOMPAT_OVERRIDE_PROP_TREE_FILE[] =
+        "/dev/__properties__/appcompat_override/property_info";
 using namespace std::literals;
 
 using android::base::ErrnoError;
@@ -1280,11 +1284,17 @@
         return;
     }
 
-    constexpr static const char kPropertyInfosPath[] = "/dev/__properties__/property_info";
-    if (!WriteStringToFile(serialized_contexts, kPropertyInfosPath, 0444, 0, 0, false)) {
+    if (!WriteStringToFile(serialized_contexts, PROP_TREE_FILE, 0444, 0, 0, false)) {
         PLOG(ERROR) << "Unable to write serialized property infos to file";
     }
-    selinux_android_restorecon(kPropertyInfosPath, 0);
+    selinux_android_restorecon(PROP_TREE_FILE, 0);
+
+    mkdir(APPCOMPAT_OVERRIDE_PROP_FOLDERNAME, S_IRWXU | S_IXGRP | S_IXOTH);
+    if (!WriteStringToFile(serialized_contexts, APPCOMPAT_OVERRIDE_PROP_TREE_FILE, 0444, 0, 0,
+                           false)) {
+        PLOG(ERROR) << "Unable to write vendor overrides to file";
+    }
+    selinux_android_restorecon(APPCOMPAT_OVERRIDE_PROP_TREE_FILE, 0);
 }
 
 static void ExportKernelBootProps() {