Add option to use Ada code in romstage

If selected, libgnat is linked into romstage. In addition, a call to
romstage_adainit() is added to support Ada program data
initialization.

BUG=b:252792591
BRANCH=firmware-brya-14505.B
TEST=Ada code compiles for romstage and loads successfully

Change-Id: I74f0460f6b14fde2b4bd6391e1782b2e5b217707
Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70274
Reviewed-by: Tarun Tuli <taruntuli@google.com>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Makefile

@@ -316,6 +316,9 @@ $(eval $(postinclude-hooks))
 $(foreach class,$(classes),$(eval $(class)-srcs:=$(sort $($(class)-srcs))))
 
 # Build Kconfig .ads if necessary
+ifeq ($(CONFIG_ROMSTAGE_ADA),y)
+romstage-srcs += $(obj)/romstage/$(notdir $(KCONFIG_AUTOADS))
+endif
 ifeq ($(CONFIG_RAMSTAGE_ADA),y)
 ramstage-srcs += $(obj)/ramstage/$(notdir $(KCONFIG_AUTOADS))
 endif

src/cpu/intel/car/romstage.c

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <adainit.h>
 #include <arch/romstage.h>
 #include <arch/symbols.h>
 #include <commonlib/helpers.h>
@@ -40,6 +41,18 @@ void __noreturn romstage_main(void)
 	if (CONFIG(VBOOT_EARLY_EC_SYNC))
 		vboot_sync_ec();
 
+	/*
+	 * We can generally jump between C and Ada code back and forth
+	 * without trouble. But since we don't have an Ada main() we
+	 * have to do some Ada package initializations that GNAT would
+	 * do there. This has to be done before calling any Ada code.
+	 *
+	 * The package initializations should not have any dependen-
+	 * cies on C code. So we can call them here early, and don't
+	 * have to worry at which point we can start to use Ada.
+	 */
+	romstage_adainit();
+
 	mainboard_romstage_entry();
 
 	/* Check the stack. */

src/include/adainit.h

@@ -15,6 +15,12 @@
  * lizations automatically. When not, we have to call it explicitly.
  */
 
+#if CONFIG(ROMSTAGE_ADA)
+void romstage_adainit(void);
+#else
+static inline void romstage_adainit(void) {}
+#endif
+
 #if CONFIG(RAMSTAGE_ADA)
 void ramstage_adainit(void);
 #else

src/lib/Kconfig

@@ -5,6 +5,11 @@ config MISSING_BOARD_RESET
 	  implementation. This activates a stub that logs the missing
 	  board reset and halts execution.
 
+config ROMSTAGE_ADA
+	bool
+	help
+	  Selected by features that use Ada code in romstage.
+
 config RAMSTAGE_ADA
 	bool
 	help

src/lib/Makefile.inc

@@ -339,6 +339,7 @@ $(objcbfs)/%.debug.rmod: $(objcbfs)/%.debug | $(RMODTOOL)
 $(obj)/%.elf.rmod: $(obj)/%.elf | $(RMODTOOL)
 	$(RMODTOOL) -i $< -o $@
 
+romstage-$(CONFIG_ROMSTAGE_ADA) += cb.ads
 ramstage-$(CONFIG_RAMSTAGE_ADA) += cb.ads
 
 ifeq ($(CONFIG_RAMSTAGE_LIBHWBASE),y)

src/lib/gnat/Makefile.inc

@@ -51,6 +51,9 @@ $(foreach arch,$(standard-archs), \
 $(foreach arch,$(standard-archs), \
 	$(eval $(call libgnat-template,$(arch))))
 
+ifeq ($(CONFIG_ROMSTAGE_ADA),y)
+romstage-libs += $(obj)/libgnat-$(ARCH-romstage-y)/libgnat.a
+endif
 ifeq ($(CONFIG_RAMSTAGE_ADA),y)
 ramstage-libs += $(obj)/libgnat-$(ARCH-ramstage-y)/libgnat.a
 endif