VTS LTP Workflow
================

A Guide to Developing LTP for VTS/Android

What is LTP?
------------

[Github](https://github.com/linux-test-project/ltp) (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$ make distclean`
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

You can update these files manually, or you can run a script which regenerates
these files from scratch, external/ltp/android/tools/gen_android_build.sh.

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.

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](https://qa-reports.linaro.org/android-lkft/).

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](https://buganizer.corp.google.com/hotlists/733268).

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](https://lists.linux.it/listinfo/ltp). 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.