kbuild: kselftest - new make target to build and run kernel selftests

Add a new make target "kselftest" to enable kernel testing. This
new target builds and runs kernel selftests. Running as root is
recommended for a complete test run as some tests don't run when
run by non-root user. Build, install, and boot kernel before
running kselftest on it.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Makefile

@@ -1027,6 +1027,13 @@ headers_check: headers_install
 	$(Q)$(MAKE) $(hdr-inst)=include/uapi HDRCHECK=1
 	$(Q)$(MAKE) $(hdr-inst)=arch/$(hdr-arch)/include/uapi/asm $(hdr-dst) HDRCHECK=1
 
+# ---------------------------------------------------------------------------
+# Kernel selftest
+
+PHONY += kselftest
+kselftest:
+	$(Q)$(MAKE) -C tools/testing/selftests run_tests
+
 # ---------------------------------------------------------------------------
 # Modules
 
@@ -1230,6 +1237,11 @@ help:
 	@echo  '  headerdep       - Detect inclusion cycles in headers'
 	@$(MAKE) -f $(srctree)/scripts/Makefile.help checker-help
 	@echo  ''
+	@echo  'Kernel selftest'
+	@echo  '  kselftest       - Build and run kernel selftest (run as root)'
+	@echo  '                    Build, install, and boot kernel before'
+	@echo  '                    running kselftest on it'
+	@echo  ''
 	@echo  'Kernel packaging:'
 	@$(MAKE) $(build)=$(package-dir) help
 	@echo  ''