As per a discussion with Muhammad Usama Anjum [1], the following is how
one is supposed to build selftests:

    make headers && make -C tools/testing/selftests/mm

Change the selftest build system's lib.mk to fail out with a helpful
message if that prerequisite "make headers" has not been done yet.

[1] https://lore.kernel.org/all/bf910fa5-0c96-3707-cce4-5bcc656b6274@collabora.com/

[jhubbard@nvidia.com: abort the make process the first time headers aren't detected]
  Link: https://lkml.kernel.org/r/14573e7e-f2ad-ff34-dfbd-3efdebee51ed@nvidia.com
[anders.roxell@linaro.org: fix out-of-tree builds]
  Link: https://lkml.kernel.org/r/20230613074931.666966-1-anders.roxell@linaro.org
Link: https://lkml.kernel.org/r/20230606071637.267103-12-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Add missing cases for the i386 and x86_64 architectures when
determining the LLVM target for building kselftest.

Fixes: 795285ef2425 ("selftests: Fix clang cross compilation")
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

We are missing a ) when we attempt to complain about not having enough
configuration for clang, resulting in the rather inscrutable error:

../lib.mk:23: *** unterminated call to function 'error': missing ')'.  Stop.

Add the required ) so we print the message we were trying to print.

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Pull Kselftest updates from Shuah Khan:
 "Several fixes and enhancements to existing tests and a few new tests:

   - add new amd-pstate tests and fix and enhance existing ones

   - add new watchdog tests and enhance existing ones to improve
     coverage

   - fixes to ftrace, splice_read, rtc, and efivars tests

   - fixes to handle egrep obsolescence in the latest grep release

   - miscellaneous spelling and SPDX fixes"

* tag 'linux-kselftest-next-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest: (24 commits)
  selftests/ftrace: Use long for synthetic event probe test
  selftests/tpm2: Split async tests call to separate shell script runner
  selftests: splice_read: Fix sysfs read cases
  selftests: ftrace: Use "grep -E" instead of "egrep"
  selftests: gpio: Use "grep -E" instead of "egrep"
  selftests: kselftest_deps: Use "grep -E" instead of "egrep"
  selftests/efivarfs: Add checking of the test return value
  cpufreq: amd-pstate: fix spdxcheck warnings for amd-pstate-ut.c
  selftests: rtc: skip when RTC is not present
  selftests/ftrace: event_triggers: wait longer for test_event_enable
  selftests/vDSO: Add riscv getcpu & gettimeofday test
  Documentation: amd-pstate: Add tbench and gitsource test introduction
  selftests: amd-pstate: Trigger gitsource benchmark and test cpus
  selftests: amd-pstate: Trigger tbench benchmark and test cpus
  selftests: amd-pstate: Split basic.sh into run.sh and basic.sh.
  selftests: amd-pstate: Rename amd-pstate-ut.sh to basic.sh.
  selftests/ftrace: Convert tracer tests to use 'requires' to specify program dependency
  selftests/ftrace: Add check for ping command for trigger tests
  selftests/watchdog: Fix spelling mistake "Temeprature" -> "Temperature"
  selftests/watchdog: add test for WDIOC_GETTEMP
  ...

When exporting and running a subset of selftests via kselftest, files from
parts of the source tree which were not exported are not available. A few
tests are trying to source such files. Address the problem by using
symlinks.

The problem can be reproduced by running:
make -C tools/testing/selftests gen_tar TARGETS="drivers/net/bonding"
[... extract archive ...]
./run_kselftest.sh

or:
make kselftest KBUILD_OUTPUT=/tmp/kselftests TARGETS="drivers/net/bonding"

Fixes: bbb774d921e2 ("net: Add tests for bonding and team address list management")
Fixes: eccd0a80dc7f ("selftests: net: dsa: add a stress test for unlocked FDB operations")
Link: https://lore.kernel.org/netdev/40f04ded-0c86-8669-24b1-9a313ca21076@redhat.com/
Reported-by: Jonathan Toppins <jtoppins@redhat.com>
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Reviewed-by: Jonathan Toppins <jtoppins@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

This change enables to extend CFLAGS and LDFLAGS from command line, e.g.
to extend compiler checks: make USERCFLAGS=-Werror USERLDFLAGS=-static

USERCFLAGS and USERLDFLAGS are documented in
Documentation/kbuild/makefiles.rst and Documentation/kbuild/kbuild.rst

This should be backported (down to 5.10) to improve previous kernel
versions testing as well.

Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220909103901.1503436-1-mic@digikod.net
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

These changes simplify the Makefile and handle these 5 ways to build
Landlock tests:
- make -C tools/testing/selftests/landlock
- make -C tools/testing/selftests TARGETS=landlock gen_tar
- make TARGETS=landlock kselftest-gen_tar
- make TARGETS=landlock O=build kselftest-gen_tar
- make -C /tmp/linux TARGETS=landlock O=/tmp/build kselftest-gen_tar

This also makes $(KHDR_INCLUDES) available to other test collections
when building in their directory.

Fixes: f1227dc7d041 ("selftests/landlock: fix broken include of linux/landlock.h")
Fixes: 3bb267a36185 ("selftests: drop khdr make target")
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Guillaume Tucker <guillaume.tucker@collabora.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220909103402.1501802-1-mic@digikod.net

When we stopped using KSFT_KHDR_INSTALL, a side effect is we also
changed the value of `top_srcdir`. This can be seen by looking at the
code removed by commit 49de12ba06ef
("selftests: drop KSFT_KHDR_INSTALL make target").

(Note though that this commit didn't break this, technically the one
before it did since that's the one that stopped KSFT_KHDR_INSTALL from
being used, even though the code was still there.)

Previously lib.mk reconfigured `top_srcdir` when KSFT_KHDR_INSTALL was
being used. Now, that's no longer the case.

As a result, the path to gup_test.h in vm/Makefile was wrong, and
since it's a dependency of all of the vm binaries none of them could
be built. Instead, we'd get an "error" like:

    make[1]: *** No rule to make target
        '/[...]/tools/testing/selftests/vm/compaction_test', needed by
	'all'.  Stop.

So, modify lib.mk so it once again sets top_srcdir to the root of the
kernel tree.

Fixes: f2745dc0ba3d ("selftests: stop using KSFT_KHDR_INSTALL")
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Drop the KSFT_KHDR_INSTALL make target now that all use-cases have
been removed from the other kselftest Makefiles.

Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Unlike GCC clang uses a single compiler image to support multiple target
architectures meaning that we can't simply rely on CROSS_COMPILE to select
the output architecture. Instead we must pass --target to the compiler to
tell it what to output, kselftest was not doing this so cross compilation
of kselftest using clang resulted in kselftest being built for the host
architecture.

More work is required to fix tests using custom rules but this gets the
bulk of things building.

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>