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android / platform / packages / modules / SdkExtensions / refs/heads/android12-dev
commitb5b5f0300e2ca2e08417d01f49775c12e41826d3[log] [tgz]
authorTreeHugger Robot <[email protected]>Fri Aug 06 16:53:38 2021 +0000
committerAndroid (Google) Code Review <[email protected]>Fri Aug 06 16:53:38 2021 +0000
treeb9251322b945c26e995305c3dc0fda359587af85
parent98a26ccd9e93e9aff0300250fa471fdd7b20c280 [diff]
parent26198b71800cefc4ee285a2cb808653c9a34ecea [diff]
Merge "Write generated data to a temp file first, attempt #2." into sc-dev
tree: b9251322b945c26e995305c3dc0fda359587af85
  1. derive_classpath/
  2. derive_sdk/
  3. framework/
  4. gen_sdk/
  5. testing/
  6. tests/
  7. Android.bp
  8. com.android.sdkext.avbpubkey
  9. com.android.sdkext.pem
  10. com.android.sdkext.pk8
  11. com.android.sdkext.x509.pem
  12. manifest.json
  13. OWNERS
  14. PREUPLOAD.cfg
  15. README.md
  16. TEST_MAPPING
README.md

SdkExtensions module

SdkExtensions module is responsible for:

  • deciding the extension SDK level of the device;
  • providing APIs for applications to query the extension SDK level;
  • determining the values for the BOOTCLASSPATH, DEX2OATBOOTCLASSPATH, and SYSTEMSERVERCLASSPATH environment variables.

General information

Structure

The module is packaged in an apex, com.android.sdkext, and has several components:

  • bin/derive_classpath: a native binary that runs early in the device boot process. It reads individual classpath configs files from the system and other modules, merges them, and defines the definition of *CLASSPATH environ variables.
  • bin/derive_sdk: native binary that runs early in the device boot process and reads metadata of other modules, to set system properties relating to the extension SDK (for instance build.version.extensions.r).
  • javalib/framework-sdkextension.jar: this is a jar on the bootclasspath that exposes APIs to applications to query the extension SDK level.

Deriving extension SDK level

derive_sdk is a program that reads metadata stored in other apex modules, in the form of binary protobuf files in subpath etc/sdkinfo.pb inside each apex. The structure of this protobuf can be seen here. The exact steps for converting a set of metadata files to actual extension versions is likely to change over time, and should not be depended upon.

Reading extension SDK level

The module exposes a java class SdkExtensions in the package android.os.ext. The method getExtensionVersion(int) can be used to read the version of a particular sdk extension, e.g. getExtensionVersion(Build.VERSION_CODES.R).

Deriving classpaths

derive_classpath service reads and merges individual config files in the /system/etc/classpaths/ and /apex/*/etc/classpaths. Each config stores protobuf message from classpaths.proto in a proto binary format. Exact merging algorithm that determines the order of the classpath entries is described in derive_classpath.cpp and may change over time.

Developer information

Adding a new extension version

For every new Android SDK level a new extension version should be defined. These are the steps necessary to do that:

  • Add the new modules in this extension version to the SdkModule enum in sdk.proto.
  • Update derive_sdk.cpp by:
  • mapping the modules' package names to the new enum values
  • creating a new set with the new enum values
  • set a new sysprop to the value of GetSdkLevel with the new enum set
  • add a unit test to derive_sdk_test.cpp verifying the new extensions works
  • Make the SdkExtensions.getExtensionVersion API support the new extensions.
  • Extend the CTS test to verify the above two behaviors.
  • Update RollbackManagerServiceImpl#getExtensionVersions to account for the new extension version.