diff --git a/cmds/idmap2/idmap2d/Idmap2Service.cpp b/cmds/idmap2/idmap2d/Idmap2Service.cpp
index d723776..15e22a3 100644
--- a/cmds/idmap2/idmap2d/Idmap2Service.cpp
+++ b/cmds/idmap2/idmap2d/Idmap2Service.cpp
@@ -33,22 +33,29 @@
 #include "idmap2/BinaryStreamVisitor.h"
 #include "idmap2/FileUtils.h"
 #include "idmap2/Idmap.h"
-#include "idmap2/Policies.h"
+#include "idmap2/Result.h"
 #include "idmap2/SysTrace.h"
+#include "idmap2/ZipFile.h"
 #include "utils/String8.h"
 
 using android::IPCThreadState;
+using android::base::StringPrintf;
 using android::binder::Status;
 using android::idmap2::BinaryStreamVisitor;
+using android::idmap2::GetPackageCrc;
 using android::idmap2::Idmap;
 using android::idmap2::IdmapHeader;
-using android::idmap2::PolicyBitmask;
+using android::idmap2::ZipFile;
 using android::idmap2::utils::kIdmapCacheDir;
 using android::idmap2::utils::kIdmapFilePermissionMask;
 using android::idmap2::utils::UidHasWriteAccessToPath;
 
+using PolicyBitmask = android::ResTable_overlayable_policy_header::PolicyBitmask;
+
 namespace {
 
+constexpr const char* kFrameworkPath = "/system/framework/framework-res.apk";
+
 Status ok() {
   return Status::ok();
 }
@@ -62,6 +69,21 @@
   return static_cast<PolicyBitmask>(arg);
 }
 
+Status GetCrc(const std::string& apk_path, uint32_t* out_crc) {
+  const auto zip = ZipFile::Open(apk_path);
+  if (!zip) {
+    return error(StringPrintf("failed to open apk %s", apk_path.c_str()));
+  }
+
+  const auto crc = GetPackageCrc(*zip);
+  if (!crc) {
+    return error(crc.GetErrorMessage());
+  }
+
+  *out_crc = *crc;
+  return ok();
+}
+
 }  // namespace
 
 namespace android::os {
@@ -93,21 +115,52 @@
   return ok();
 }
 
-Status Idmap2Service::verifyIdmap(const std::string& overlay_apk_path,
-                                  int32_t fulfilled_policies ATTRIBUTE_UNUSED,
-                                  bool enforce_overlayable ATTRIBUTE_UNUSED,
-                                  int32_t user_id ATTRIBUTE_UNUSED, bool* _aidl_return) {
+Status Idmap2Service::verifyIdmap(const std::string& target_apk_path,
+                                  const std::string& overlay_apk_path, int32_t fulfilled_policies,
+                                  bool enforce_overlayable, int32_t user_id ATTRIBUTE_UNUSED,
+                                  bool* _aidl_return) {
   SYSTRACE << "Idmap2Service::verifyIdmap " << overlay_apk_path;
   assert(_aidl_return);
+
   const std::string idmap_path = Idmap::CanonicalIdmapPathFor(kIdmapCacheDir, overlay_apk_path);
   std::ifstream fin(idmap_path);
   const std::unique_ptr<const IdmapHeader> header = IdmapHeader::FromBinaryStream(fin);
   fin.close();
-  *_aidl_return = header && header->IsUpToDate();
+  if (!header) {
+    *_aidl_return = false;
+    return error("failed to parse idmap header");
+  }
 
-  // TODO(b/119328308): Check that the set of fulfilled policies of the overlay has not changed
+  uint32_t target_crc;
+  if (target_apk_path == kFrameworkPath && android_crc_) {
+    target_crc = *android_crc_;
+  } else {
+    auto target_crc_status = GetCrc(target_apk_path, &target_crc);
+    if (!target_crc_status.isOk()) {
+      *_aidl_return = false;
+      return target_crc_status;
+    }
 
-  return ok();
+    // Loading the framework zip can take several milliseconds. Cache the crc of the framework
+    // resource APK to reduce repeated work during boot.
+    if (target_apk_path == kFrameworkPath) {
+      android_crc_ = target_crc;
+    }
+  }
+
+  uint32_t overlay_crc;
+  auto overlay_crc_status = GetCrc(overlay_apk_path, &overlay_crc);
+  if (!overlay_crc_status.isOk()) {
+    *_aidl_return = false;
+    return overlay_crc_status;
+  }
+
+  auto up_to_date =
+      header->IsUpToDate(target_apk_path.c_str(), overlay_apk_path.c_str(), target_crc, overlay_crc,
+                         ConvertAidlArgToPolicyBitmask(fulfilled_policies), enforce_overlayable);
+
+  *_aidl_return = static_cast<bool>(up_to_date);
+  return *_aidl_return ? ok() : error(up_to_date.GetErrorMessage());
 }
 
 Status Idmap2Service::createIdmap(const std::string& target_apk_path,
@@ -137,21 +190,27 @@
     return error("failed to load apk " + overlay_apk_path);
   }
 
-  const auto idmap = Idmap::FromApkAssets(target_apk_path, *target_apk, overlay_apk_path,
-                                          *overlay_apk, policy_bitmask, enforce_overlayable);
+  const auto idmap =
+      Idmap::FromApkAssets(*target_apk, *overlay_apk, policy_bitmask, enforce_overlayable);
   if (!idmap) {
     return error(idmap.GetErrorMessage());
   }
 
+  // idmap files are mapped with mmap in libandroidfw. Deleting and recreating the idmap guarantees
+  // that existing memory maps will continue to be valid and unaffected.
+  unlink(idmap_path.c_str());
+
   umask(kIdmapFilePermissionMask);
   std::ofstream fout(idmap_path);
   if (fout.fail()) {
     return error("failed to open idmap path " + idmap_path);
   }
+
   BinaryStreamVisitor visitor(fout);
   (*idmap)->accept(&visitor);
   fout.close();
   if (fout.fail()) {
+    unlink(idmap_path.c_str());
     return error("failed to write to idmap path " + idmap_path);
   }
 
diff --git a/cmds/idmap2/idmap2d/Idmap2Service.h b/cmds/idmap2/idmap2d/Idmap2Service.h
index 73a236a..abee999 100644
--- a/cmds/idmap2/idmap2d/Idmap2Service.h
+++ b/cmds/idmap2/idmap2d/Idmap2Service.h
@@ -20,9 +20,6 @@
 #include <android-base/unique_fd.h>
 #include <binder/BinderService.h>
 
-#include <optional>
-#include <string>
-
 #include "android/os/BnIdmap2.h"
 
 namespace android::os {
@@ -34,18 +31,24 @@
   }
 
   binder::Status getIdmapPath(const std::string& overlay_apk_path, int32_t user_id,
-                              std::string* _aidl_return);
+                              std::string* _aidl_return) override;
 
   binder::Status removeIdmap(const std::string& overlay_apk_path, int32_t user_id,
-                             bool* _aidl_return);
+                             bool* _aidl_return) override;
 
-  binder::Status verifyIdmap(const std::string& overlay_apk_path, int32_t fulfilled_policies,
-                             bool enforce_overlayable, int32_t user_id, bool* _aidl_return);
+  binder::Status verifyIdmap(const std::string& target_apk_path,
+                             const std::string& overlay_apk_path, int32_t fulfilled_policies,
+                             bool enforce_overlayable, int32_t user_id,
+                             bool* _aidl_return) override;
 
   binder::Status createIdmap(const std::string& target_apk_path,
                              const std::string& overlay_apk_path, int32_t fulfilled_policies,
                              bool enforce_overlayable, int32_t user_id,
-                             std::optional<std::string>* _aidl_return);
+                             std::optional<std::string>* _aidl_return) override;
+
+ private:
+  // Cache the crc of the android framework package since the crc cannot change without a reboot.
+  std::optional<uint32_t> android_crc_;
 };
 
 }  // namespace android::os
diff --git a/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl b/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl
index cd474c0..156f1d7 100644
--- a/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl
+++ b/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl
@@ -20,18 +20,13 @@
  * @hide
  */
 interface IIdmap2 {
-  const int POLICY_PUBLIC = 0x00000001;
-  const int POLICY_SYSTEM_PARTITION = 0x00000002;
-  const int POLICY_VENDOR_PARTITION = 0x00000004;
-  const int POLICY_PRODUCT_PARTITION = 0x00000008;
-  const int POLICY_SIGNATURE = 0x00000010;
-  const int POLICY_ODM_PARTITION = 0x00000020;
-  const int POLICY_OEM_PARTITION = 0x00000040;
-
   @utf8InCpp String getIdmapPath(@utf8InCpp String overlayApkPath, int userId);
   boolean removeIdmap(@utf8InCpp String overlayApkPath, int userId);
-  boolean verifyIdmap(@utf8InCpp String overlayApkPath, int fulfilledPolicies,
-                      boolean enforceOverlayable, int userId);
+  boolean verifyIdmap(@utf8InCpp String targetApkPath,
+					  @utf8InCpp String overlayApkPath,
+                      int fulfilledPolicies,
+                      boolean enforceOverlayable,
+                      int userId);
   @nullable @utf8InCpp String createIdmap(@utf8InCpp String targetApkPath,
                                           @utf8InCpp String overlayApkPath,
                                           int fulfilledPolicies,
diff --git a/cmds/idmap2/idmap2d/aidl/android/os/OverlayablePolicy.aidl b/cmds/idmap2/idmap2d/aidl/android/os/OverlayablePolicy.aidl
new file mode 100644
index 0000000..02b27a8
--- /dev/null
+++ b/cmds/idmap2/idmap2d/aidl/android/os/OverlayablePolicy.aidl
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2019 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.os;
+
+/**
+ * @see ResourcesTypes.h ResTable_overlayable_policy_header::PolicyFlags
+ * @hide
+ */
+interface OverlayablePolicy {
+  const int PUBLIC = 0x00000001;
+  const int SYSTEM_PARTITION = 0x00000002;
+  const int VENDOR_PARTITION = 0x00000004;
+  const int PRODUCT_PARTITION = 0x00000008;
+  const int SIGNATURE = 0x00000010;
+  const int ODM_PARTITION = 0x00000020;
+  const int OEM_PARTITION = 0x00000040;
+  const int ACTOR_SIGNATURE = 0x00000080;
+}