Directories, Rules, and sepolicy

This page describes the directory layout for devices running Android 8.0 and higher, VNDK rules, and associated sepolicy.

Directory layout

The Degenerated Directory Layout consists of the following directories:

  • /system/lib[64] contains all framework shared libraries, including LL-NDK, VNDK, and framework-only libraries (including LL-NDK-Private and some libraries with the same names as the ones in VNDK-SP).
  • /system/lib[64]/vndk-sp contains VNDK-SP libraries for same-process HALs.
  • /vendor/lib[64] contains the extended VNDK libraries (either DXUA or DXUX VNDK libraries), same-process HAL implementations, and other vendor shared libraries.
  • /vendor/lib[64]/vndk-sp may contain extra libraries that are used by VNDK-SP libraries.

Vendor modules load the VNDK libraries from /system/lib[64].

VNDK rules

This section provides a comprehensive list of VNDK rules:

  • Framework processes must not load non-SP-HAL shared libraries from vendor partitions (not strictly enforced in Android O but will be in a future release).
  • Vendor processes must not load non-LL-NDK, non-VNDK-SP, and non-VNDK libraries from the system partition. (not strictly enforced in Android O but will be in a future release).
  • Installed VNDK libraries must be a subset of Google-defined eligible VNDK libraries.
  • The outer dependencies of SP-HAL and SP-HAL-Dep must be restricted to LL-NDK or Google-defined VNDK-SP libraries.
    • The dependencies of an SP-HAL shared library must be restricted to LL-NDK libraries, Google-defined VNDK-SP libraries, other SP-HAL libraries, and/or other vendor shared libraries that can be labeled as SP-HAL-Dep libraries.
    • A vendor shared library can be labeled as a SP-HAL-Dep library only if it is not an AOSP library and its dependencies are restricted to LL-NDK libraries, Google-defined VNDK-SP libraries, SP-HAL libraries, and/or other SP-HAL-Dep libraries.
  • VNDK-SP must be self-contained. libRS_internal.so gets special treatment in Android 8.0, but will be revisited in a future release.
  • No framework-vendor communication through non-HIDL interfaces, including (but not limited to) binder, sockets, shared memories, files, etc.
  • The size of the system partition must be large enough to contain two copies of all eligible VNDK libraries and a copy of ineligible framework shared libraries.

sepolicy

Framework processes described in this section correspond to coredomain in sepolicies while vendor processes correspond to non-coredomain. For example, /dev/binder can be accessed only in coredomain and /dev/vndbinder can be accessed only in non-coredomain.

Similar policies restrict the access to the shared libraries on system and vendor partitions. The following table shows the rights to access shared libraries of different categories:

Category Partition Accessible from
coredomain
Accessible from
non-coredomain
LL-NDK System Y Y
LL-NDK-Private System Y Y
VNDK-SP/VNDK-SP-Private System Y Y
VNDK-SP-Ext Vendor Y Y
VNDK System Y Y
VNDK-Ext Vendor N Y
FWK-ONLY System Y N
FWK-ONLY-RS System Y N
SP-HAL Vendor Y Y
SP-HAL-Dep Vendor Y Y
VND-ONLY Vendor N Y

LL-NDK-Private and VNDK-SP-Private must be accessible from both domains because non-coredomain will indirectly access them. Similarly, SP-HAL-Dep must be accessible from coredomain because SP-HAL relies on it.