Invalidate idmap when target updates

When the target package update, check if the idmap file must change.
If so, propagate the idmap changes to the targets overlay paths, and
invalidate cached overlay ApkAssets in ResourcesManager.

Bug: 147794117
Bug: 150877400
Test: OverlayRemountedTest
Test: libandroidfw_tests
Change-Id: I6115c30bae3672b188a5ff270720a0eea15b43b5

1 files changed, 6 insertions, 0 deletions

diff --git a/cmds/idmap2/idmap2d/Idmap2Service.cpp b/cmds/idmap2/idmap2d/Idmap2Service.cpp
index e55ea6c00545..75fc7f714ce3 100644
--- a/cmds/idmap2/idmap2d/Idmap2Service.cpp
+++ b/cmds/idmap2/idmap2d/Idmap2Service.cpp
@@ -149,15 +149,21 @@ Status Idmap2Service::createIdmap(const std::string& target_apk_path,
     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);
   }