VTS LTP Workflow

A Guide to Developing LTP for VTS/Android

What is LTP?

Github (upstream)

LTP (Linux Test Project) is a suite of tests that covers both kernel interfaces and userspace functionality (glibc, commonly used binaries, etc). For the purposes of Android the userspace functionality testing is of less importance and in fact much of it must be disabled, given the functionality is not available in Android.

As of mid-2018 there are on the order of 900 tests executed in VTS. Most tests are run in both 32-bit and 64-bit mode. Many more are available but currently disabled due to either being broken or not applicable on Android.

How is LTP Run in VTS?

The LTP source is located at external/ltp in the Android tree. This is not an exact mirror of upstream, there are outstanding changes to LTP for it to work on Android which have not yet been pushed upstream. In addition to the LTP source there is also the VTS wrapper around it. This is located at test/vts-testcase/kernel/ltp. Some noteworthy directories/files:

• external/ltp/android/: Contains Android-specific files, aside from Android.[bp, mk] at top level.
• external/ltp/android/Android.ltp.mk: Lists build rules for the LTP modules built under make. This file gets auto-generated by android/tools/gen_android_build.sh.
• external/ltp/gen.bp: Lists build rules for the LTP modules built under Soong. This file gets auto-generated by android/tools/gen_android_build.sh.
• external/ltp/android/ltp_package_list.mk: Lists all tests that will get pulled into VTS - VTS depends on this list. This file gets auto-generated by android/tools/gen_android_build.sh.
• external/ltp/android/tools/disabled_tests.txt: Lists tests which cannot or should not be compiled for Android. This file is read by gen_android_build.sh during LTP upgrades to produce *.mk files required to build LTP for Android.
• external/ltp/testcases: Source for LTP tests. Among the most important for the purposes of Treble are those in external/ltp/testcases/kernel/syscalls.
• test/vts-testcase/kernel/ltp/configs/disabled_tests.py: Any test listed here will not be run in VTS, either in the staging or stable set, despite being compiled. If a test does not appear here then it at least runs as part of the VtsKernelLtpStaging module.
• test/vts-testcase/kernel/ltp/configs/stable_tests.py: Any test listed here will run as part of the VtsKernelLtp (stable) module.

New tests are run in the staging set for some time (a couple weeks or more) to ensure they are reliable prior to their being added to the stable set.

To run VTS LTP it must first be built. VTS is not device specific, you need not compile it specifically for the device you wish to run it on, assuming it is the same architecture.

• . build/envsetup.sh
• lunch
• make -j vts

Before running VTS ensure your host has the required prerequisites (this need only be done once):

• . test/vts/script/setup.sh

Then open vts-tradefed and run the VTS stable set:

• vts-tradefed
• vts-tf > run vts-kernel -m VtsKernelLtp

If you regularly work with multiple devices it may be useful to specify the specific device you wish to run VTS on via the serial number:

• vts-tf > run vts-kernel -m VtsKernelLtp -s 000123456789

Or we can run the staging set:

• vts-tf > run vts-kernel -m VtsKernelLtpStaging

Or a specific test within the stable set:

• vts-tf > run vts-kernel -m VtsKernelLtp -t dio.dio13

Maybe several:

• vts-tf > run vts-kernel -m VtsKernelLtp -t dio.dio13,fs.stream04

You may choose whether to specify bitness of the tests. This would run 4 tests - dio.dio13 both 32-bit and 64-bit, fs.stream04 64-bit, and fs.lftest01 32-bit:

• vts-tf > run vts-kernel -m VtsKernelLtp -t dio.dio13,fs.stream04_64bit,fs.lftest01_32bit

Running LTP Faster

Running LTP tests within VTS can be quite cumbersome, especially if you are iterating a lot trying to debug something. Build and run LTP tests faster by doing

• external/ltp$ mma
• external/ltp$ adb sync data

The test cases will be located at /data/nativetest{64,}/ltp/testcases/bin.

Sometimes you need to perform this step after syncing:

• external/ltp$ git clean -x -f -d Otherwise, build will fail.

In order to simulate the exact environment that VTS will be creating for each of these tests, you can set the following environment variables before you run the test. This is very useful if the test itself depends on some of these variables to be set appropriately.

• adb root && adb shell

In the root shell on device:

• mkdir -p /data/local/tmp/ltp/tmp/ltptemp
• mkdir -p /data/local/tmp/ltp/tmp/tmpbase
• mkdir -p /data/local/tmp/ltp/tmp/tmpdir
• restorecon -F -R /data/local/tmp/ltp
• export TMP=/data/local/tmp/ltp/tmp
• export LTPTMP=/data/local/tmp/ltp/tmp/ltptemp
• export LTP_DEV_FS_TYPE=ext4
• export TMPBASE=/data/local/tmp/ltp/tmp/tmpbase
• export TMPDIR=/data/local/tmp/ltp/tmp/tmpdir
• export LTPROOT=/data/local/tmp/ltp

For running 64-bit tests:

• export PATH=/data/nativetest64/ltp/testcases/bin:$PATH

Or For running 32-bit tests:

• export PATH=/data/nativetest/ltp/testcases/bin:$PATH

How do I enable or disable tests from the LTP build?

Tests are disabled from the LTP build by adding them to external/ltp/android/tools/disabled_tests.txt. Many tests have been added to this file over time. Some of them are not applicable to Android and therefore should not be built. Others were disabled here because they were failing at one point in time for reasons unknown.

To make a change to what is built in LTP, add or remove an entry in this file, and then update the Android-specific build files for LTP, mentioned above:

• external/ltp/android/Android.ltp.mk, for LTP modules built in make
• external/ltp/gen.bp, for LTP modules built in soong
• external/ltp/android/ltp_package_list.mk, which lists all LTP modules that get pulled into VTS

Update these files by running the script located at external/ltp/android/tools/gen_android_build.sh. Instructions for the script are in external/ltp/android/how-to-update.txt.

How do I enable or disable tests from VTS LTP?

In addition to whether modules are built in external/ltp, it is also necessary to configure the VTS harness for LTP to determine which tests are in the stable set, the staging set, or disabled. Note that being disabled in VTS does not affect whether the test is built, but rather determines whether it is run at all as part of the stable or staging sets.

The file test/vts-testcase/kernel/ltp/configs/stable_tests.py lists tests that will run as part of VTS stable (VtsKernelLtp). The test/vts-testcase/kernel/ltp/configs/disabled_tests.py file lists tests that are runtime disabled in VTS. If a test is not listed in either of these files, but is enabled in the build in external/ltp, then it is in the staging set (VtsKernelLtpStaging).

When a test is enabled for the first time in VTS it should be in the staging set. The behavior of the test will be observed over a period of time and ensure the test is reliable. After a period of time (a week or two) it will be moved to the stable set.

Tests that will never be relevant to Android should be disabled from the build in external/ltp. Tests that are (hopefully) temporarily broken should be runtime disabled in VTS. The staging and stable sets should normally all be passing. If something is failing there it should either be fixed with priority or disabled until it can be fixed.

If the runtime of LTP changes significantly be sure to update the runtime-hint and test-timeout parameters to VTS in test/vts-testcase/kernel/ltp/stable/AndroidTest.xml.

How do I see or get notified about recent VTS LTP results?

The internal portal at go/vts-web shows results for the continuous VTS testing done on internal devices. By adding tests such as VtsKernelLtp or VtsKernelLtpStaging to your favorites you will get email notifications whenever failures are seen. Be warned, the testing iterates continuously and the notification emails can generate a lot of traffic.

Test results are also gathered by Linaro and may be seen here.

Help! The external/ltp build is failing!

Try doing a make distclean inside of external/ltp. If an upgrade to LTP has recently merged or the build files were recently updated, stale files in external/ltp can cause build failures.

What outstanding issues exist?

The hotlist for LTP bugs is ltp-todo.

When you begin working on an LTP bug please assign the bug to yourself so that others know it is being worked on.

Testing x86_64

It is not advisable to run LTP tests directly on your host unless you are fully aware of what the tests will do and are okay with it. These tests may destabilize your box or cause data loss. If you need to run tests on an x86 platform and are unsure if they are safe you should run them in emulation, in a virtualized environment, or on a dedicated development x86 platform.

Sending Fixes Upstream

The mailing list for LTP is located here. Some standard kernel guidelines apply to sending patches; they should be checkpatch (scripts/checkpatch.pl in the kernel repository) clean and sent in plain text in canonical patch format. One easy way to do this is by using git format-patch and git send-email.

There is an #LTP channel on freenode. The maintainer Cyril Hrubis is there (his nick is metan).

Merging Fixes

When possible please merge fixes upstream first. Then cherrypick the change onto aosp/master in external/ltp.