selftests: add memfd_create() + sealing tests

Some basic tests to verify sealing on memfds works as expected and
guarantees the advertised semantics.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Ryan Lortie <desrt@desrt.ca>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Daniel Mack <zonque@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/selftests/Makefile

@@ -2,6 +2,7 @@ TARGETS = breakpoints
 TARGETS += cpu-hotplug
 TARGETS += efivarfs
 TARGETS += kcmp
+TARGETS += memfd
 TARGETS += memory-hotplug
 TARGETS += mqueue
 TARGETS += net

tools/testing/selftests/memfd/.gitignore

+memfd_test
+memfd-test-file

tools/testing/selftests/memfd/Makefile

+uname_M := $(shell uname -m 2>/dev/null || echo not)
+ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/)
+ifeq ($(ARCH),i386)
+	ARCH := X86
+endif
+ifeq ($(ARCH),x86_64)
+	ARCH := X86
+endif
+
+CFLAGS += -I../../../../arch/x86/include/generated/uapi/
+CFLAGS += -I../../../../arch/x86/include/uapi/
+CFLAGS += -I../../../../include/uapi/
+CFLAGS += -I../../../../include/
+
+all:
+ifeq ($(ARCH),X86)
+	gcc $(CFLAGS) memfd_test.c -o memfd_test
+else
+	echo "Not an x86 target, can't build memfd selftest"
+endif
+
+run_tests: all
+ifeq ($(ARCH),X86)
+	gcc $(CFLAGS) memfd_test.c -o memfd_test
+endif
+	@./memfd_test || echo "memfd_test: [FAIL]"
+
+clean:
+	$(RM) memfd_test