Earlier attempts to get "make O=build kselftest-all" to work were
not successful as they made undesirable changes to some functions
in the top-level Makefile.  This series takes a different
approach by removing the root cause of the problem within
kselftest, which is when the sub-Makefile tries to install kernel
headers "backwards" by calling make with the top-level Makefile.
The actual issue comes from the fact that $(srctree) is ".." when
building in a sub-directory with "O=build" which then obviously
makes "-C $(top_srcdir)" point outside of the real source tree.

With this series, the generic kselftest targets work as expected
from the top level with or without a build directory e.g.:

  $ make kselftest-all

  $ make O=build kselftest-all

Then in order to build using the sub-Makefile explicitly, the
headers have to be installed first.  This is arguably a valid
requirement to have when building a tool from a sub-Makefile.
For example, "make -C tools/testing/nvdimm/" fails in a similar
way until <asm/rwonce.h> has been generated by a kernel build.

v2: replace headers_install with headers

Guillaume Tucker (4):
  selftests: drop khdr make target
  selftests: stop using KSFT_KHDR_INSTALL
  selftests: drop KSFT_KHDR_INSTALL make target
  Makefile: add headers to kselftest targets

 Makefile                                      |  4 +-
 tools/testing/selftests/Makefile              | 28 +-------------
 tools/testing/selftests/arm64/mte/Makefile    |  1 -
 tools/testing/selftests/arm64/signal/Makefile |  1 -
 .../selftests/arm64/signal/test_signals.h     |  4 +-
 .../selftests/drivers/s390x/uvdevice/Makefile |  1 -
 .../selftests/futex/functional/Makefile       |  1 -
 tools/testing/selftests/kvm/Makefile          |  1 -
 tools/testing/selftests/landlock/Makefile     |  1 -
 tools/testing/selftests/lib.mk                | 38 -------------------
 tools/testing/selftests/net/Makefile          |  1 -
 tools/testing/selftests/net/mptcp/Makefile    |  1 -
 tools/testing/selftests/tc-testing/Makefile   |  1 -
 tools/testing/selftests/vm/Makefile           |  1 -
 14 files changed, 5 insertions(+), 79 deletions(-)

--
2.30.2

On 7/12/22 2:29 AM, Guillaume Tucker wrote:
> Earlier attempts to get "make O=build kselftest-all" to work were
> not successful as they made undesirable changes to some functions
> in the top-level Makefile.  This series takes a different
> approach by removing the root cause of the problem within
> kselftest, which is when the sub-Makefile tries to install kernel
> headers "backwards" by calling make with the top-level Makefile.
> The actual issue comes from the fact that $(srctree) is ".." when
> building in a sub-directory with "O=build" which then obviously
> makes "-C $(top_srcdir)" point outside of the real source tree.
> 
> With this series, the generic kselftest targets work as expected
> from the top level with or without a build directory e.g.:
> 
>    $ make kselftest-all
> 
>    $ make O=build kselftest-all
> 
> Then in order to build using the sub-Makefile explicitly, the
> headers have to be installed first.  This is arguably a valid
> requirement to have when building a tool from a sub-Makefile.
> For example, "make -C tools/testing/nvdimm/" fails in a similar
> way until <asm/rwonce.h> has been generated by a kernel build.
> 
> v2: replace headers_install with headers
> 

I already applied the series. Please send me patches I can apply
on top of the ones in linux-kselftest next branch.

thanks,
-- Shuah