VNDK Definition Tool

The VNDK definition tool helps vendors migrate their source tree to an Android 8.0 environment. This tool scans binary files in the system and vendor images then resolves dependencies. Based on the module dependency graph, the tool can also detect violations to VNDK concepts and provide insight/suggestions for moving modules between partitions. If an Generic System Image (GSI) is specified, the VNDK definition tool can compare your system image with the GSI and determine the extended libraries.

This section covers three frequently used commands for the VNDK definition tool:

vndk. Compute VNDK_SP_LIBRARIES, VNDK_SP_EXT_LIBRARIES, and EXTRA_VENDOR_LIBRARIES for build system workaround in Android 8.0 and higher.
check-dep. Check the violating module dependencies from vendor modules to non-eligible framework shared libraries.
deps. Print the dependencies between the shared libraries and executables.

For more details on advanced command usage, refer to README.md file in the VNDK Definition Tool repository.

vndk

The vndk subcommand loads the shared libraries and executables from the system partition and vendor partitions, then resolves module dependencies to determine the libraries that must be copied to /system/lib[64]/vndk-sp-${VER} and /vendor/lib[64]. Options for the vndk subcommand include:

Option	Description
`--system`	Point to a directory containing the files that will reside in the system partition.
`--vendor`	Point to a directory containing the files that will reside in a vendor partition.
`--aosp-system`	Point to a directory containing the files that will reside in the Generic System Image (GSI).
`--load-extra-deps`	Point to a file that describes the implicit dependencies, such as `dlopen()`.

For example, to compute the VNDK library sets, run the following vndk subcommand:

./vndk_definition_tool.py vndk \
    --system ${ANDROID_PRODUCT_OUT}/system \
    --vendor ${ANDROID_PRODUCT_OUT}/vendor \
    --aosp-system ${ANDROID_PRODUCT_OUT}/../generic_arm64_ab/system\
    --load-extra-deps dlopen.dep

Specify extra dependencies with a simple file format. Each line represents a relationship, with the file before the colon depending on the file after the colon. For example:

/system/lib/libart.so: /system/lib/libart-compiler.so

This line lets the VNDK definition tool know that libart.so depends on libart-compiler.so.

Installation destination

VNDK definition tool lists libraries and corresponding install directories for the following categories:

Category	Directory
vndk_sp	Must install to `/system/lib[64]/vndk-sp-${VER}`
vndk_sp_ext	Must install to `/vendor/lib[64]/vndk-sp`
extra_vendor_libs	Must install to `/vendor/lib[64]`

Build system templates

After gathering outputs from VNDK definition tool, a vendor can create an Android.mk and fill in VNDK_SP_LIBRARIES, VNDK_SP_EXT_LIBRARIES and EXTRA_VENDOR_LIBRARIES to automate the process to copy libraries to the designated installation destination.

ifneq ($(filter $(YOUR_DEVICE_NAME),$(TARGET_DEVICE)),)
VNDK_SP_LIBRARIES := ##_VNDK_SP_##
VNDK_SP_EXT_LIBRARIES := ##_VNDK_SP_EXT_##
EXTRA_VENDOR_LIBRARIES := ##_EXTRA_VENDOR_LIBS_##

#-------------------------------------------------------------------------------
# VNDK Modules
#-------------------------------------------------------------------------------
LOCAL_PATH := $(call my-dir)

define define-vndk-lib
include $$(CLEAR_VARS)
LOCAL_MODULE := $1.$2
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_PREBUILT_MODULE_FILE := $$(TARGET_OUT_INTERMEDIATE_LIBRARIES)/$1.so
LOCAL_STRIP_MODULE := false
LOCAL_MULTILIB := first
LOCAL_MODULE_TAGS := optional
LOCAL_INSTALLED_MODULE_STEM := $1.so
LOCAL_MODULE_SUFFIX := .so
LOCAL_MODULE_RELATIVE_PATH := $3
LOCAL_VENDOR_MODULE := $4
include $$(BUILD_PREBUILT)

ifneq ($$(TARGET_2ND_ARCH),)
ifneq ($$(TARGET_TRANSLATE_2ND_ARCH),true)
include $$(CLEAR_VARS)
LOCAL_MODULE := $1.$2
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_PREBUILT_MODULE_FILE := $$($$(TARGET_2ND_ARCH_VAR_PREFIX)TARGET_OUT_INTERMEDIATE_LIBRARIES)/$1.so
LOCAL_STRIP_MODULE := false
LOCAL_MULTILIB := 32
LOCAL_MODULE_TAGS := optional
LOCAL_INSTALLED_MODULE_STEM := $1.so
LOCAL_MODULE_SUFFIX := .so
LOCAL_MODULE_RELATIVE_PATH := $3
LOCAL_VENDOR_MODULE := $4
include $$(BUILD_PREBUILT)
endif  # TARGET_TRANSLATE_2ND_ARCH is not true
endif  # TARGET_2ND_ARCH is not empty
endef

$(foreach lib,$(VNDK_SP_LIBRARIES),\
    $(eval $(call define-vndk-lib,$(lib),vndk-sp-gen,vndk-sp,)))
$(foreach lib,$(VNDK_SP_EXT_LIBRARIES),\
    $(eval $(call define-vndk-lib,$(lib),vndk-sp-ext-gen,vndk-sp,true)))
$(foreach lib,$(EXTRA_VENDOR_LIBRARIES),\
    $(eval $(call define-vndk-lib,$(lib),vndk-ext-gen,,true)))


#-------------------------------------------------------------------------------
# Phony Package
#-------------------------------------------------------------------------------

include $(CLEAR_VARS)
LOCAL_MODULE := $(YOUR_DEVICE_NAME)-vndk
LOCAL_MODULE_TAGS := optional
LOCAL_REQUIRED_MODULES := \
    $(addsuffix .vndk-sp-gen,$(VNDK_SP_LIBRARIES)) \
    $(addsuffix .vndk-sp-ext-gen,$(VNDK_SP_EXT_LIBRARIES)) \
    $(addsuffix .vndk-ext-gen,$(EXTRA_VENDOR_LIBRARIES))
include $(BUILD_PHONY_PACKAGE)

endif  # ifneq ($(filter $(YOUR_DEVICE_NAME),$(TARGET_DEVICE)),)

check-dep

The check-dep subcommand scans vendor modules and checks their dependencies. If it detects violations, it prints the violating dependant library and symbol usages:

./vndk_definition_tool.py check-dep \
    --system ${ANDROID_PRODUCT_OUT}/system \
    --vendor ${ANDROID_PRODUCT_OUT}/vendor \
    --tag-file eligible-list.csv \
    --module-info ${ANDROID_PRODUCT_OUT}/module-info.json \
    1> check_dep.txt \
    2> check_dep_err.txt

For example, the following sample output shows a violating dependency from libRS_internal.so to libmediandk.so:

/system/lib/libRS_internal.so
        MODULE_PATH: frameworks/rs
        /system/lib/libmediandk.so
                AImageReader_acquireNextImage
                AImageReader_delete
                AImageReader_getWindow
                AImageReader_new
                AImageReader_setImageListener

Options for the check-dep subcommand include:

Option	Description
`--tag-file`	Must refer to an eligible library tag file (described below), which is a Google-provided spreadsheet that described categories of framework shared libraries.
`--module-info`	Points to the `module-info.json` generated by Android build system. It helps the VNDK definition tool associate binary modules with source code.

Eligible library tag file

Google provides an eligible VNDK spreadsheet (e.g. eligible-list.csv) that tags the framework shared libraries that can be used by vendor modules:

Tag	Description
LL-NDK	Shared libraries with stable ABIs/APIs that can be used by both framework and vendor modules.
LL-NDK-Private	Private dependencies of LL-NDK libraries. Vendor modules must not access these libraries directly.
VNDK-SP	SP-HAL framework shared libraries dependencies.
VNDK-SP-Private	VNDK-SP dependencies that are not directly accessible to all vendor modules.
VNDK	Framework shared libraries that are available to vendor modules (except SP-HAL and SP-HAL-Dep).
VNDK-Private	VNDK dependencies that are not directly accessible to all vendor modules.
FWK-ONLY	Framework-only shared libraries that must not be accessed by vendor modules (neither directly nor indirectly).
FWK-ONLY-RS	Framework-only shared libraries that must not be accessed by vendor modules (except for RS usages).

The following table describes tags used for vendor shared libraries:

Tag	Description
SP-HAL	Same-process HAL implementation shared libraries.
SP-HAL-Dep	SP-HAL vendor shared libraries dependencies (a.k.a. SP-HAL dependencies excluding LL-NDK and VNDK-SP).
VND-ONLY	Framework-invisible shared libraries that must not be accessed by framework modules. The copied extended VNDK libraries will be tagged as VND-ONLY as well.

Relationships between tags:

Figure 1. Relationships between tags.

deps

To debug the library dependencies, the deps subcommand prints the module dependencies:

./vndk_definition_tool.py deps \
    --system ${ANDROID_PRODUCT_OUT}/system \
    --vendor ${ANDROID_PRODUCT_OUT}/vendor

The output consists of multiple lines. The line without a tab character starts a new section. The line with a tab character depends on the preceding section. For example:

/system/lib/ld-android.so
/system/lib/libc.so
        /system/lib/libdl.so

This output shows that ld-android.so does not have a dependency and libc.so depends on libdl.so.

When specifying the --revert option, deps subcommand prints the usages of libraries (reversed dependencies):

./vndk_definition_tool.py deps \
    --revert \
    --system ${ANDROID_PRODUCT_OUT}/system \
    --vendor ${ANDROID_PRODUCT_OUT}/vendor

For example:

/system/lib/ld-android.so
        /system/lib/libdl.so

This output shows that ld-android.so is used by libdl.so, or in other words, libdl.so depends on ld-android.so. In addition, this output shows that libdl.so is the sole user of ld-android.so.

When specifying the --symbol option, the deps subcommand prints the symbols being used:

./vndk_definition_tool.py deps \
    --symbol \
    --system ${ANDROID_PRODUCT_OUT}/system \
    --vendor ${ANDROID_PRODUCT_OUT}/vendor

For example:

/system/lib/libc.so
        /system/lib/libdl.so
                android_get_application_target_sdk_version
                dl_unwind_find_exidx
                dlclose
                dlerror
                dlopen
                dlsym

This output shows that libc.so depends on 6 functions exported from libdl.so. If both the --symbol option and --revert option are specified, the symbols used by the user will be printed.