Re: [PATCH v2 1/2] selftests: run tests on nommu architecture

[Hajime Tazaki <thehajime@gmail.com>]

Hello,

On Tue, 25 Aug 2026 22:36:22 +0900,
Lorenzo Stoakes (ARM) wrote:

> > 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?

on nommu we cannot use /bin/bash (i.e., no fork(2) so, we use
/bin/hash, a busybox-offered shell with vfork.
with this `cd -` (standards specified) isn't implemented due to slim
requirement of that shell (I suppose, miserable...).

thus this workaround.

> >  	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'?

thanks, I will remove CONFIG_ part.

initially I was trying to pull generated/autoconf.h into kselftest but
it doesn't do much compared to many modifications (run_kselftest.sh
needs to run independently from build tree) so, I used this macro but,
yes, it's confusing.

> > +	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.

yes, in addition to moving to selftests/nommu this can be more cleaner
initial introduction of this target.

thanks for reviewing.

-- Hajime