On FDE devices, initialize user 0

Fix ugly special cases for user 0: initialize them explicitly.

Bug: 26704408
Change-Id: I1b8536b9e5e87ea98b4009a309f2e22c56006651

init/builtins.cpp

@@ -884,6 +884,13 @@ static int do_installkey(const std::vector<std::string>& args) {
                                      do_installkeys_ensure_dir_exists);
 }
 
+static int do_init_user0(const std::vector<std::string>& args) {
+    if (!is_file_crypto()) {
+        return 0;
+    }
+    return e4crypt_do_init_user0();
+}
+
 BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
     constexpr std::size_t kMax = std::numeric_limits<std::size_t>::max();
     static const Map builtin_functions = {
@@ -900,6 +907,7 @@ BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
         {"export",                  {2,     2,    do_export}},
         {"hostname",                {1,     1,    do_hostname}},
         {"ifup",                    {1,     1,    do_ifup}},
+        {"init_user0",              {0,     0,    do_init_user0}},
         {"insmod",                  {1,     kMax, do_insmod}},
         {"installkey",              {1,     1,    do_installkey}},
         {"load_persist_props",      {0,     0,    do_load_persist_props}},

rootdir/init.rc

@@ -420,6 +420,8 @@ on post-fs-data
 
     symlink /data/data /data/user/0
 
+    init_user0
+
     # Reload policy from /data/security if present.
     setprop selinux.reload_policy 1