On Tue, Aug 25, 2026 at 10:59:44AM +0900, Hajime Tazaki wrote: > Architectures lacks MMU doesn't support fork(2) syscall and only > vfork(2) is available with limitations. Thus, we cannot run kselftest > on nommu architecture as is. > > This commit addresses this issue with the following changes: > > - on build stage, add -DCONFIG_NOMMU to CFLAGS when NOMMU=1 variable > added to the build/make argument. > - on test run stage, avoid calling timeout command when NOMMU=1 variable > added to environmental variable, since timeout command uses fork > syscall which nommu platform doesn't support. > - kselftest_harness.h: skip the tests if the file is include when > executing on NOMMU platform, as there is no fork(2) syscall. > - replace "cd -" use as it is not available a shell supported on nommu > (e.g., busybox hush), use cd "$OLDDIR" instead. > - describe the difference of nommu tests in the document. > > So command line to build/execute tests for nommu should be like below: > > $ make ARCH=um NOMMU=1 O=build kselftest-all TARGETS=mm/nommu > $ make ARCH=um NOMMU=1 O=build kselftest-install TARGETS=mm/nommu > $ NOMMU=1 ./build/kselftest/kselftest_install/run_kselftest.sh -p \ > -c mm/nommu > > Cc: Shuah Khan <[email protected]> > Cc: Jonathan Corbet <[email protected]> > Cc: Kees Cook <[email protected]> > Cc: Andy Lutomirski <[email protected]> > Cc: Will Drewry <[email protected]> > Cc: Mark Brown <[email protected]> > Cc: Brendan Jackman <[email protected]> > Cc: Hangbin Liu <[email protected]> > Cc: "Ricardo B. Marliere" <[email protected]> > Cc: [email protected] > Cc: [email protected] > Cc: [email protected] > Cc: [email protected] > Closes: > https://sashiko.dev/#/patchset/20260813063401.1786548-1-thehajime%40gmail.com > Signed-off-by: Hajime Tazaki <[email protected]>
Doesn't seem too crazy, but some nitty comments below. > > -- > > rfc => v2 > - reformat ktap header, reported by Sashiko review > > rfc: > https://lore.kernel.org/linux-mm/[email protected]/ > --- > Documentation/dev-tools/kselftest.rst | 14 ++++++++++++++ > tools/testing/selftests/kselftest/runner.sh | 9 +++++++-- > tools/testing/selftests/kselftest_harness.h | 4 ++++ > tools/testing/selftests/lib.mk | 8 ++++++++ > 4 files changed, 33 insertions(+), 2 deletions(-) > > diff --git a/Documentation/dev-tools/kselftest.rst > b/Documentation/dev-tools/kselftest.rst > index 64c0ec7428a2..a65f3ebc5906 100644 > --- a/Documentation/dev-tools/kselftest.rst > +++ b/Documentation/dev-tools/kselftest.rst > @@ -230,6 +230,20 @@ section:: > > .. _tar's auto-compress: > https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress > > +Build and test on nommu target > +============================== > + > +If you (cross-)build kselftests for nommu targets, or run tests on nommu > targets, use > +``NOMMU=1`` as a make variable/environment setting to tell build system to > do the additional > +checks. These nommu targets may differ in several ways, such as not > supporting fork(2) or > +using musl or another libc. Set this variable to apply the necessary build > and test adjustments. > + > +:: > + > + $ make ARCH=um NOMMU=1 O=build kselftest-all TARGETS=mm/nommu # <= > build-only > + $ make ARCH=um NOMMU=1 O=build kselftest-install TARGETS=mm/nommu > + $ NOMMU=1 ./build/kselftest/kselftest_install/run_kselftest.sh -p -c > mm/nommu > + > Contributing new tests > ====================== > > diff --git a/tools/testing/selftests/kselftest/runner.sh > b/tools/testing/selftests/kselftest/runner.sh > index 311811dc55a0..7287d8290b6c 100644 > --- a/tools/testing/selftests/kselftest/runner.sh > +++ b/tools/testing/selftests/kselftest/runner.sh > @@ -38,8 +38,12 @@ tap_prefix() > > tap_timeout() > { > + # nommu doesn't support timeout command (missing fork(2)) > + if [ "$NOMMU" = "1" ] ; then > + echo "timeout isn't supported for nommu" > + $1 > # Make sure tests will time out if utility is available. > - if [ -x /usr/bin/timeout ] ; then > + elif [ -x /usr/bin/timeout ] ; then > /usr/bin/timeout --foreground "$kselftest_timeout" \ > /usr/bin/timeout "$kselftest_timeout" $1 > else > @@ -130,6 +134,7 @@ run_one() > return $KSFT_FAIL > fi > fi > + OLDDIR=$(pwd) > cd `dirname $TEST` > /dev/null > (((( tap_timeout "$cmd" 2>&1; echo $? >&3) | > tap_prefix >&4) 3>&1) | > @@ -147,7 +152,7 @@ run_one() > *) > ktap_test_fail "$TEST_HDR_MSG # exit=$rc";; > esac > - cd - >/dev/null > + cd "$OLDDIR" >/dev/null Hmm, why are you changing this bit? > fi > > return $rc > diff --git a/tools/testing/selftests/kselftest_harness.h > b/tools/testing/selftests/kselftest_harness.h > index 261e4df94d9d..0d05946a5e7a 100644 > --- a/tools/testing/selftests/kselftest_harness.h > +++ b/tools/testing/selftests/kselftest_harness.h > @@ -1274,6 +1274,10 @@ static int test_harness_run(int argc, char **argv) > unsigned int count = 0; > unsigned int pass_count = 0; > > +#ifdef CONFIG_NOMMU Let's not prefix with CONFIG_ :) I think this is pretty confusing vs. the kernel CONFIG_xxx flags, esp. as this obviously inverts CONFIG_MMU. maybe just 'NOMMU'? > + ksft_print_header(); > + ksft_exit_skip("kselftest harness requires fork(2), unavailable on > NOMMU\n"); > +#endif /* CONFIG_NOMMU */ > ret = test_harness_argv_check(argc, argv); > if (ret != KSFT_PASS) > return ret; > diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk > index f02cc8a2e4ae..fdb895967768 100644 > --- a/tools/testing/selftests/lib.mk > +++ b/tools/testing/selftests/lib.mk > @@ -97,6 +97,14 @@ TEST_GEN_PROGS := $(patsubst > %,$(OUTPUT)/%,$(TEST_GEN_PROGS)) > TEST_GEN_PROGS_EXTENDED := $(patsubst > %,$(OUTPUT)/%,$(TEST_GEN_PROGS_EXTENDED)) > TEST_GEN_FILES := $(patsubst %,$(OUTPUT)/%,$(TEST_GEN_FILES)) > > +# detect if users request NOMMU build or not > +# User can set NOMMU to 1 to build/test for NOMMU platforms > +NOMMU ?= 0 > +ifeq ($(NOMMU),1) > +CFLAGS += -DCONFIG_NOMMU > +export NOMMU > +endif > + I wonder if this could be put into testing/selftests/nommu/something.mk? Though I guess would have to be included for all builds to account for nommu trying to build any kind of tests. > all: $(TEST_GEN_PROGS) $(TEST_GEN_PROGS_EXTENDED) $(TEST_GEN_FILES) \ > $(if $(TEST_GEN_MODS_DIR),gen_mods_dir) > > -- > 2.43.0 > -- Cheers, Lorenzo
