selftests: Introduce Makefile variable to list shared bash scripts

Some tests written in bash source other files in a parent directory. For
example, drivers/net/bonding/dev_addr_lists.sh sources
net/forwarding/lib.sh. If a subset of tests is exported and run outside the
source tree (for example by using `make -C tools/testing/selftests gen_tar
TARGETS="drivers/net/bonding"`), these other files must be made available
as well.

Commit ae108c48b5d2 ("selftests: net: Fix cross-tree inclusion of scripts")
addressed this problem by symlinking and copying the sourced files but this
only works for direct dependencies. Commit 25ae948b4478 ("selftests/net:
add lib.sh") changed net/forwarding/lib.sh to source net/lib.sh. As a
result, that latter file must be included as well when the former is
exported. This was not handled and was reverted in commit 2114e83381d3
("selftests: forwarding: Avoid failures to source net/lib.sh"). In order to
allow reinstating the inclusion of net/lib.sh from net/forwarding/lib.sh,
add a mechanism to list dependent files in a new Makefile variable and
export them. This allows sourcing those files using the same expression
whether tests are run in-tree or exported.

Dependencies are not resolved recursively so transitive dependencies must
be listed in TEST_INCLUDES. For example, if net/forwarding/lib.sh sources
net/lib.sh; the Makefile related to a test that sources
net/forwarding/lib.sh from a parent directory must list:
TEST_INCLUDES := \
	../../../net/forwarding/lib.sh \
	../../../net/lib.sh

v2:
Fix rst syntax in Documentation/dev-tools/kselftest.rst (Jakub Kicinski)

v1 (from RFC):
* changed TEST_INCLUDES to take relative paths, like other TEST_* variables
  (Vladimir Oltean)
* preserved common "$(MAKE) OUTPUT=... -C ... target" ordering in Makefile
  (Petr Machata)

Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/Documentation/dev-tools/kselftest.rst b/Documentation/dev-tools/kselftest.rst
index ab376b316c36..522214c7b43b 100644
--- a/Documentation/dev-tools/kselftest.rst
+++ b/Documentation/dev-tools/kselftest.rst
@@ -255,9 +255,21 @@ Contributing new tests (details)
 
    TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the
    executable which is not tested by default.
+
    TEST_FILES, TEST_GEN_FILES mean it is the file which is used by
    test.
 
+   TEST_INCLUDES is similar to TEST_FILES, it lists files which should be
+   included when exporting or installing the tests, with the following
+   differences:
+
+    * symlinks to files in other directories are preserved
+    * the part of paths below tools/testing/selftests/ is preserved when
+      copying the files to the output directory
+
+   TEST_INCLUDES is meant to list dependencies located in other directories of
+   the selftests hierarchy.
+
  * First use the headers inside the kernel source and/or git repo, and then the
    system headers.  Headers for the kernel release as opposed to headers
    installed by the distro on the system should be the primary focus to be able