On Tue, Aug 25, 2026 at 10:37:41AM +0200, David Hildenbrand (Arm) wrote: > 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/[email protected]/ > > > > 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.
I mean I think at this point with mm/nommu/nommu_xxx.c it'd make more sense to simply have selftests/nommu/ + update the mm makefile to not build stuff that's broken on nommu there. That way positively nommu-stuff is put in its own place and what's broken on mm specific to nommu can be fixed there. I'd rather isolate them clearly rather than having them live in a subdirectory of mm. > > -- > Cheers, > > David -- Cheers, Lorenzo
