Linker namespace upload
- 2. 2 Agenda • Target & Behavior • Implementation
- 3. 3 Target & Behavior Target • Reduce the possibility that 3rd APK call non- public NDK API Behavior • Non-system app will fail on N device if it uses non-public APIs. • Preloaded system app is allowed to use non- public APIs.
- 4. 4 Namespace Creation– Daemon process Only Default namespace Run native executable file Bionic execve Kernel Sys_exec ve StartLoad er /system/bin /linker Create a default Namespace and put all so into the namespace
- 5. 5 Namespace Creation – Java App Add Name Space in Linker • Default namespace • Anonymous namespace • Class-loader namespace Run Java APK Framework Fork zygote Load Dex file Create JIT Get default Namespace libart-compiler.so libvixl.so Load *.classes.dexunder default namespace Get Classloader for apk Create Anonymous Namespace Create classloader Namespace System.load to load a lib Loaded in classloader namespace Anonymous Namespace Default Namespace classloader Namespace
- 6. 6 Implementation – Name space Namespace Directory Default default_library_paths: System/lib Vendor/lib permitted_paths_: none Anonymous default_library_paths_: Same as default_library_paths of class-loader namespace. permitted_paths_: none It is used by JIT when JIT tries to load a lib. Class-loader default_library_paths： /data/app/com.eXXX- 1/lib/arm(x86);XXXX permitted_paths_: /data;XXXX
- 7. 7 Check Name space before library is loaded Caller belongs to Default namespace? Load so Whether so is in public name space list? Can be loaded No Yes Check whether *.so in the dedicated directory contained by namespace Yes No Yes Can not be loaded No
- 8. 8 Why we need it • Different constrictions on library is required for different caller. • Different constrictions on library is required for different stage for a process.