[PATCH] selftests/mm: make libnuma-dependent tests optional

The mm selftests Makefile unconditionally builds three test binaries
that depend on libnuma (migration, ksm_tests, rmap). When libnuma-dev
is not installed, the build fails with a hard error, inconsistent with
how the optional liburing dependency is already handled via
check_config.sh.

These three tests hard-depend on libnuma at both compile time
(#include <numa.h>) and link time (-lnuma), confirmed by grepping all
.c files under tools/testing/selftests/mm/ for numa.h/numaif.h, which
matches exactly ksm_tests.c, migration.c, and rmap.c.

Extend check_config.sh to probe for libnuma via a compile-plus-link
check (the link check needs a main() symbol), gate the three tests in
TEST_GEN_FILES behind NUMA_EXTRA_LIBS, and print a warning when
libnuma is missing. The liburing section is switched from ">" to ">>"
writes and both output files are truncated once at the top, so the new
libnuma section can append without overwriting the liburing section.

Signed-off-by: Jiangshan Yi <[email protected]>
---
 tools/testing/selftests/mm/Makefile        | 21 +++++++++--
 tools/testing/selftests/mm/check_config.sh | 44 +++++++++++++++++++---
 2 files changed, 57 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index e6df968f0971..235c8ec788a7 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -75,7 +75,9 @@ ifneq (,$(filter $(ARCH),arm64 riscv riscv64 x86 x86_64 loongarch32 loongarch64)
 TEST_GEN_FILES += memfd_secret
 endif
 TEST_GEN_FILES += memory-failure
+ifneq ($(NUMA_EXTRA_LIBS),)
 TEST_GEN_FILES += migration
+endif
 TEST_GEN_FILES += mkdirty
 TEST_GEN_FILES += mlock-random-test
 TEST_GEN_FILES += mlock2-tests
@@ -94,7 +96,9 @@ TEST_GEN_FILES += uffd-stress
 TEST_GEN_FILES += uffd-unit-tests
 TEST_GEN_FILES += uffd-wp-mremap
 TEST_GEN_FILES += split_huge_page_test
+ifneq ($(NUMA_EXTRA_LIBS),)
 TEST_GEN_FILES += ksm_tests
+endif
 TEST_GEN_FILES += ksm_functional_tests
 TEST_GEN_FILES += mdwe_test
 TEST_GEN_FILES += hugetlb_fault_after_madv
@@ -103,7 +107,9 @@ TEST_GEN_FILES += hugetlb_dio
 TEST_GEN_FILES += droppable
 TEST_GEN_FILES += guard-regions
 TEST_GEN_FILES += merge
+ifneq ($(NUMA_EXTRA_LIBS),)
 TEST_GEN_FILES += rmap
+endif
 TEST_GEN_FILES += folio_split_race_test
 
 ifneq ($(ARCH),arm64)
@@ -256,11 +262,11 @@ $(OUTPUT)/gup_longterm: LDLIBS += $(IOURING_EXTRA_LIBS)
 
 $(OUTPUT)/mlock-random-test $(OUTPUT)/memfd_secret: LDLIBS += -lcap
 
-$(OUTPUT)/ksm_tests: LDLIBS += -lnuma
+$(OUTPUT)/ksm_tests: LDLIBS += $(NUMA_EXTRA_LIBS)
 
-$(OUTPUT)/migration: LDLIBS += -lnuma
+$(OUTPUT)/migration: LDLIBS += $(NUMA_EXTRA_LIBS)
 
-$(OUTPUT)/rmap: LDLIBS += -lnuma
+$(OUTPUT)/rmap: LDLIBS += $(NUMA_EXTRA_LIBS)
 
 local_config.mk local_config.h: check_config.sh
 	$(call msg,CHK,config,$@)
@@ -277,6 +283,15 @@ warn_missing_liburing:
 	echo
 endif
 
+ifeq ($(NUMA_EXTRA_LIBS),)
+all: warn_missing_libnuma
+
+warn_missing_libnuma:
+	@echo ; \
+	echo "Warning: missing libnuma support. Some tests (migration, ksm_tests, rmap) will be skipped." ; \
+	echo
+endif
+
 ifneq ($(PAGE_FRAG_WARNING),)
 all: warn_missing_page_frag
 
diff --git a/tools/testing/selftests/mm/check_config.sh b/tools/testing/selftests/mm/check_config.sh
index 32beaefe279e..8e6d1616561b 100755
--- a/tools/testing/selftests/mm/check_config.sh
+++ b/tools/testing/selftests/mm/check_config.sh
@@ -7,10 +7,17 @@
 OUTPUT_H_FILE=local_config.h
 OUTPUT_MKFILE=local_config.mk
 
+# Truncate output files so that re-running this script does not
+# accumulate duplicate content (all writes below use append ">>").
+: > $OUTPUT_H_FILE
+: > $OUTPUT_MKFILE
+
 tmpname=$(mktemp)
 tmpfile_c=${tmpname}.c
 tmpfile_o=${tmpname}.o
 
+trap 'rm -f ${tmpname} ${tmpname}.*' EXIT
+
 # liburing
 echo "#include <sys/types.h>"        > $tmpfile_c
 echo "#include <liburing.h>"        >> $tmpfile_c
@@ -19,12 +26,39 @@ echo "int func(void) { return 0; }" >> $tmpfile_c
 $CC $CFLAGS -c $tmpfile_c -o $tmpfile_o >/dev/null 2>&1
 
 if [ -f $tmpfile_o ]; then
-    echo "#define LOCAL_CONFIG_HAVE_LIBURING 1"  > $OUTPUT_H_FILE
-    echo "IOURING_EXTRA_LIBS = -luring"          > $OUTPUT_MKFILE
+    echo "#define LOCAL_CONFIG_HAVE_LIBURING 1"  >> $OUTPUT_H_FILE
+    echo "IOURING_EXTRA_LIBS = -luring"          >> $OUTPUT_MKFILE
 else
-    echo "// No liburing support found"          > $OUTPUT_H_FILE
-    echo "# No liburing support found, so:"      > $OUTPUT_MKFILE
+    echo "// No liburing support found"          >> $OUTPUT_H_FILE
+    echo "# No liburing support found, so:"      >> $OUTPUT_MKFILE
     echo "IOURING_EXTRA_LIBS = "                >> $OUTPUT_MKFILE
 fi
 
-rm ${tmpname}.*
+rm -f $tmpfile_o
+
+# libnuma
+echo "#include <numa.h>"            > $tmpfile_c
+echo "#include <numaif.h>"         >> $tmpfile_c
+echo "int func(void) { return 0; }" >> $tmpfile_c
+echo "int main(void) { return 0; }" >> $tmpfile_c
+
+$CC $CFLAGS -c $tmpfile_c -o $tmpfile_o >/dev/null 2>&1
+
+if [ -f $tmpfile_o ]; then
+    tmplink=${tmpname}.bin
+    # Also check linking, not just compilation, because <numa.h> may be
+    # available without the shared library (libnuma-dev vs libnuma)
+    if $CC $CFLAGS $tmpfile_c -o $tmplink -lnuma >/dev/null 2>&1; then
+        echo "#define LOCAL_CONFIG_HAVE_LIBNUMA 1"  >> $OUTPUT_H_FILE
+        echo "NUMA_EXTRA_LIBS = -lnuma"             >> $OUTPUT_MKFILE
+    else
+        echo "// No libnuma support found"          >> $OUTPUT_H_FILE
+        echo "# No libnuma support found, so:"      >> $OUTPUT_MKFILE
+        echo "NUMA_EXTRA_LIBS = "                   >> $OUTPUT_MKFILE
+    fi
+else
+    echo "// No libnuma support found"              >> $OUTPUT_H_FILE
+    echo "# No libnuma support found, so:"          >> $OUTPUT_MKFILE
+    echo "NUMA_EXTRA_LIBS = "                       >> $OUTPUT_MKFILE
+fi
+
-- 
2.25.1