Re: [PATCH v2 0/2] support kselftest on nommu platform

["David Hildenbrand (Arm)" <david@kernel.org>]

On 8/25/26 03:59, Hajime Tazaki wrote:
> We add an ability to execute kselftest on nommu platforms.
> 
> Currently there are several issues if we wish to run kselftests on nommu
> targets:
> 
> - it cannot compile/build test binaries because the current files mainly
>   assume to build with glibc,
> - some of the tests are not able to run on nommu targets as there are no
>   fork(2) syscall.
> 
> The first issue can be avoided if we can build static PIE binaries (if
> targets support it), but in our case (build on ubuntu/glibc and run on
> alpine/musl-libc), it fails to invoke due to lack of the GNU ifunc
> mechanism.  Thus, we need to cross-compile with musl toolchain, which
> needs to be solved the first issue.
> 
> The second issue is the lack of fork(2) syscall on those platforms.
> Especially the test harness helper (kselftest_harness.h) uses the
> syscall, which cannot be simply with vfork(2).  `timeout` command used
> in `runner.sh` never works for nommu platform as it uses fork(2).
> 
> nommu component in the mm subsystem has several known issues and having
> test cases should help this situation, thus this patchset is very first
> step toward enriching test environment which has not been well tested
> for a while.  The test cases is implemented based on the document
> (Documentation/admin-guide/mm/nommu-mmap.rst).
> 
> So, for the first step, nommu targets only support low-level API of
> kselftests (kselftest.h), and implement tests in a new target,
> TARGETS=mm/nommu.  Other targets are currently not even able to build
> due to toolchain issues but will be addressed once the initial
> introduction which mainly focuses on nommu test will be settled.
> 
> The patch was initially combined with other patches but is decoupled to
> only focus on test framework and testcases.
> 
> - rfc:
> https://lore.kernel.org/linux-mm/20260813063401.1786548-1-thehajime@gmail.com/
> 
> Hajime Tazaki (2):
>   selftests: run tests on nommu architecture
>   selftests/mm: add nommu mmap and mremap behavior tests
> 
>  Documentation/dev-tools/kselftest.rst         |  14 +
>  tools/testing/selftests/Makefile              |   1 +
>  tools/testing/selftests/kselftest/runner.sh   |   9 +-
>  tools/testing/selftests/kselftest_harness.h   |   4 +
>  tools/testing/selftests/lib.mk                |   8 +
>  tools/testing/selftests/mm/nommu/Makefile     |   7 +
>  .../selftests/mm/nommu/nommu_mmap_test.c      | 265 +++++++++++++
>  .../selftests/mm/nommu/nommu_mremap_test.c    | 353 ++++++++++++++++++

That's odd.

	tools/testing/selftests/mm

itself should know which tests can be built and ran on nommu. nommu-only tests
can be placed in mm/nommu, but I would expect tools/testing/selftests/mm's
Makefile and run script to compile and run only selftests that are supported on
the given platform.

-- 
Cheers,

David