tests: Add build subsystem for unit testing coreboot

Add a subsystem which will be used for writing, building and running
unit tests for different coreboot's modules. This work is built using
Cmocka unit testing framework. Description of what unit testing means
(for the author) and how unit testing framework evaluation was performed
may be found in Documentation/technotes/2020-03-unit-testing-coreboot.md

Makefiles structure is very similar to this used for building coreboot
images. Every directory has its own Makefile.inc were tests' names,
sources, subdirs and multiple other test-related attributes are defined
in form of variables.

Signed-off-by: Jan Dabros <jsd@semihalf.com>
Change-Id: I9b0220b84b9a6e448476ca3eb3ccccc5fb829ad1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39894
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

Makefile

@@ -141,6 +141,14 @@ NOMKDIR:=1
 endif
 endif
 
+ifneq ($(filter %-test %-tests,$(MAKECMDGOALS)),)
+ifneq ($(filter-out %-test %-tests, $(MAKECMDGOALS)),)
+$(error Cannot mix unit-tests targets with other targets)
+endif
+UNIT_TEST:=1
+NOCOMPILE:=
+endif
+
 .xcompile: util/xcompile/xcompile
 	rm -f $@
 	$< $(XGCCPATH) > $@.tmp
@@ -159,7 +167,9 @@ real-all:
 	@exit 1
 else
 
+ifneq ($(UNIT_TEST),1)
 include $(DOTCONFIG)
+endif
 
 # in addition to the dependency below, create the file if it doesn't exist
 # to silence stupid warnings about a file that would be generated anyway.
@@ -177,7 +187,9 @@ ifneq ($(CONFIG_MMX),y)
 CFLAGS_x86_32 += -mno-mmx
 endif
 
+ifneq ($(UNIT_TEST),1)
 include toolchain.inc
+endif
 
 strip_quotes = $(strip $(subst ",,$(subst \",,$(1))))
 # fix makefile syntax highlighting after strip macro \" "))
@@ -276,7 +288,14 @@ evaluate_subdirs= \
 # collect all object files eligible for building
 subdirs:=$(TOPLEVEL)
 postinclude-hooks :=
+
+# Don't iterate through Makefile.incs under src/ when building tests
+ifneq ($(UNIT_TEST),1)
 $(eval $(call evaluate_subdirs))
+else
+include $(TOPLEVEL)/tests/Makefile.inc
+endif
+
 ifeq ($(FAILBUILD),1)
 $(error cannot continue build)
 endif

tests/Makefile.inc

@@ -0,0 +1,136 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# This file is part of the coreboot project.
+
+testobj = $(obj)/tests
+
+TEST_DEFAULT_CONFIG = $(top)/configs/config.emulation_qemu_x86_i440fx
+TEST_DOTCONFIG = $(testobj)/.config
+TEST_KCONFIG_AUTOHEADER := $(testobj)/config.h
+TEST_KCONFIG_AUTOCONFIG := $(testobj)/auto.conf
+TEST_KCONFIG_DEPENDENCIES := $(testobj)/auto.conf.cmd
+TEST_KCONFIG_SPLITCONFIG := $(testobj)/config
+TEST_KCONFIG_TRISTATE := $(testobj)/tristate.conf
+
+TEST_CFLAGS = -include$(src)/include/kconfig.h \
+	-include$(src)/commonlib/bsd/include/commonlib/bsd/compiler.h \
+	-include $(src)/include/rules.h \
+
+# Include generic test mock headers, before original ones
+TEST_CFLAGS += -Itests/include/mocks
+
+TEST_CFLAGS += -I$(src)/include -I$(src)/commonlib/include \
+	-I$(src)/commonlib/bsd/include -I$(src)/arch/x86/include \
+
+# Path for Kconfig autoheader
+TEST_CFLAGS += -I$(dir $(TEST_KCONFIG_AUTOHEADER))
+
+TEST_CFLAGS += -std=gnu11 -Os -ffunction-sections -fdata-sections \
+	-Wl,--gc-sections -fno-builtin
+
+# Link against Cmocka
+TEST_LDFLAGS = -lcmocka
+
+# Extra attributes for unit tests, declared per test
+attributes:= srcs cflags mocks stage
+
+stages:= decompressor bootblock romstage smm verstage
+stages+= ramstage rmodule postcar libagesa
+
+alltests:=
+subdirs:= tests/arch tests/commonlib tests/console tests/cpu tests/device
+subdirs+= tests/drivers tests/ec tests/lib tests/mainboard
+subdirs+= tests/northbridge tests/security tests/soc tests/southbridge
+subdirs+= tests/superio tests/vendorcode
+
+define tests-handler
+alltests += $(1)$(2)
+$(foreach attribute,$(attributes),
+	$(eval $(1)$(2)-$(attribute) += $($(2)-$(attribute))))
+$(foreach attribute,$(attributes),
+	$(eval $(2)-$(attribute):=))
+
+# Sanity check for stage attribute value
+$(eval $(1)$(2)-stage:=$(if $($(1)$(2)-stage),$($(1)$(2)-stage),ramstage))
+$(if $(findstring $($(1)$(2)-stage), $(stages)),,
+	$(error Wrong $(1)$(2)-stage value $($(1)$(2)-stage). \
+		Check your $(dir $(1)$(2))Makefile.inc))
+endef
+
+$(call add-special-class, tests)
+$(call evaluate_subdirs)
+
+# Create actual targets for unit test binaries
+# $1 - test name
+define TEST_CC_template
+$($(1)-objs): TEST_CFLAGS+= \
+	-D__$$(shell echo $$($(1)-stage) | tr '[:lower:]' '[:upper:]')__
+$($(1)-objs): $(obj)/$(1)/%.o: $$$$*.c $(TEST_KCONFIG_AUTOHEADER)
+	mkdir -p $$(dir $$@)
+	$(HOSTCC) $(HOSTCFLAGS) $$(TEST_CFLAGS) $($(1)-cflags)  -MMD \
+		-MT $$@ -c $$< -o $$@
+
+$($(1)-bin): TEST_LDFLAGS+= $$(foreach mock,$$($(1)-mocks),-Wl,--wrap=$$(mock))
+$($(1)-bin): $($(1)-objs)
+	$(HOSTCC) $$^ $($(1)-cflags) $$(TEST_LDFLAGS) -o $$@
+
+endef
+
+$(foreach test, $(alltests), \
+	$(eval $(test)-objs:=$(addprefix $(obj)/$(test)/, \
+		$(patsubst %.c,%.o,$($(test)-srcs)))))
+$(foreach test, $(alltests), \
+	$(eval $(test)-bin:=$(obj)/$(test)/run))
+$(foreach test, $(alltests), \
+	$(eval $(call TEST_CC_template,$(test))))
+
+$(foreach test, $(alltests), \
+	$(eval all-test-objs+=$($(test)-objs)))
+$(foreach test, $(alltests), \
+	$(eval test-bins+=$($(test)-bin)))
+
+DEPENDENCIES += $(addsuffix .d,$(basename $(all-test-objs)))
+-include $(DEPENDENCIES)
+
+# Kconfig targets
+$(TEST_DOTCONFIG):
+	mkdir -p $(dir $@)
+	cp $(TEST_DEFAULT_CONFIG) $(TEST_DOTCONFIG)
+
+# Don't override default Kconfig variables, since this will affect all
+# Kconfig targets. Change them only when calling sub-make instead.
+$(TEST_KCONFIG_AUTOHEADER): TEST_KCONFIG_FLAGS:= DOTCONFIG=$(TEST_DOTCONFIG) \
+        KCONFIG_AUTOHEADER=$(TEST_KCONFIG_AUTOHEADER) \
+        KCONFIG_AUTOCONFIG=$(TEST_KCONFIG_AUTOCONFIG) \
+        KCONFIG_DEPENDENCIES=$(TEST_KCONFIG_DEPENDENCIES) \
+        KCONFIG_SPLITCONFIG=$(TEST_KCONFIG_SPLITCONFIG) \
+        KCONFIG_TRISTATE=$(TEST_KCONFIG_TRISTATE) \
+        KBUILD_DEFCONFIG=$(TEST_DEFAULT_CONFIG)
+
+$(TEST_KCONFIG_AUTOHEADER): $(TEST_DOTCONFIG) $(objutil)/kconfig/conf
+	mkdir -p $(dir $@)
+	+$(MAKE) $(TEST_KCONFIG_FLAGS) olddefconfig
+	+$(MAKE) $(TEST_KCONFIG_FLAGS) silentoldconfig
+
+$(TEST_KCONFIG_AUTOCONFIG): $(TEST_KCONFIG_AUTOHEADER)
+	true
+
+.PHONY: $(alltests) $(addprefix clean-,$(alltests))
+.PHONY: unit-tests build-unit-tests run-unit-tests clean-unit-tests
+
+$(alltests): $$($$(@)-bin)
+	./$^
+
+unit-tests: build-unit-tests run-unit-tests
+
+build-unit-tests: $(test-bins)
+
+run-unit-tests: $(alltests)
+	echo "**********************"
+	echo "   ALL TESTS PASSED"
+	echo "**********************"
+
+$(addprefix clean-,$(alltests)): clean-%:
+	rm -rf $(obj)/$*
+
+clean-unit-tests:
+	rm -rf $(testobj)