arch/x86: Simplify <arch/early_variables.h>

This enables the use of .bss section for ENV_BOOTBLOCK
and ENV_VERSTAGE even with CAR_GLOBAL_MIGRATION=y.

In practice, boards with CAR_GLOBAL_MIGRATION=y currently
build with romcc-bootblock so they will not be using .bss.

Change-Id: Ie9dc14f3e528d3e4f48304f4d7de50df448a8af6
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35016
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/arch/x86/car.ld

@@ -76,8 +76,8 @@
 	 * cbmem console. This is useful for clearing this area on a per-stage
 	 * basis when more than one stage uses cache-as-ram for CAR_GLOBALs. */
 	_car_global_start = .;
-#if !CONFIG(CAR_GLOBAL_MIGRATION)
+#if ENV_STAGE_HAS_BSS_SECTION
-	/* Allow global unitialized variables when CAR_GLOBALs are not used. */
+	/* Allow global uninitialized variables for stages without CAR teardown. */
 	*(.bss)
 	*(.bss.*)
 	*(.sbss)

src/arch/x86/include/arch/early_variables.h

@@ -20,7 +20,8 @@
 #include <commonlib/helpers.h>
 #include <stdlib.h>
 
-#if ENV_CACHE_AS_RAM && CONFIG(CAR_GLOBAL_MIGRATION)
+#if ENV_ROMSTAGE && CONFIG(CAR_GLOBAL_MIGRATION)
+
 asm(".section .car.global_data,\"w\",@nobits");
 asm(".previous");
 #ifdef __clang__
@@ -29,27 +30,6 @@ asm(".previous");
 #define CAR_GLOBAL __attribute__((used, section(".car.global_data#")))
 #endif /* __clang__ */
 
-/*
- * In stages that use CAR (verstage, C bootblock) all CAR_GLOBAL variables are
- * accessed unconditionally because cbmem is never initialized until romstage
- * when dram comes up.
- */
-#if !ENV_ROMSTAGE
-static inline void *car_get_var_ptr(void *var)
-{
-	return var;
-}
-
-static inline void *car_sync_var_ptr(void *var)
-{
-	return var;
-}
-
-static inline int car_active(void)
-{
-	return 1;
-}
-#else
 /* Get the correct pointer for the CAR global variable. */
 void *car_get_var_ptr(void *var);
 
@@ -58,7 +38,6 @@ void *car_sync_var_ptr(void *var);
 
 /* Return 1 when currently running with globals in Cache-as-RAM, 0 otherwise. */
 int car_active(void);
-#endif /* !ENV_ROMSTAGE */
 
 /* Get and set a primitive type global variable. */
 #define car_get_var(var) \
@@ -81,26 +60,25 @@ static inline size_t car_object_offset(void *ptr)
 #else
 
 /*
- * We might end up here if:
+ * For all stages other than romstage, all CAR_GLOBAL variables are accessed
- * 1. ENV_CACHE_AS_RAM is not set for the stage or
+ * unconditionally as there is no migration of symbols.
- * 2. ENV_CACHE_AS_RAM is set for the stage but CONFIG_CAR_GLOBAL_MIGRATION
- * is not set. In this case, there is no need to migrate CAR global
- * variables. But, since we might still be running out of CAR, car_active needs
- * to return 1 if ENV_CACHE_AS_RAM is set.
  */
 
 #define CAR_GLOBAL
-static inline void *car_get_var_ptr(void *var) { return var; }
-
-#if ENV_CACHE_AS_RAM
-static inline int car_active(void) { return 1; }
-#else
-static inline int car_active(void) { return 0; }
-#endif /* ENV_CACHE_AS_RAM */
-
 #define car_get_var(var) (var)
 #define car_sync_var(var) (var)
 #define car_set_var(var, val)	(var) = (val)
-#endif /* ENV_CACHE_AS_RAM && CONFIG(CAR_GLOBAL_MIGRATION) */
+
+static inline void *car_get_var_ptr(void *var)
+{
+	return var;
+}
+
+static inline int car_active(void)
+{
+	return ENV_CACHE_AS_RAM;
+}
+
+#endif
 
 #endif /* ARCH_EARLY_VARIABLES_H */

src/cpu/x86/pae/pgtbl.c

@@ -363,7 +363,7 @@ static int read_from_cbfs(const char *name, void *buf, size_t size)
 
 int paging_enable_for_car(const char *pdpt_name, const char *pt_name)
 {
-	if (!ENV_CACHE_AS_RAM)
+	if (!preram_symbols_available())
 		return -1;
 
 	if (read_from_cbfs(pdpt_name, _pdpt, REGION_SIZE(pdpt))) {
@@ -383,7 +383,7 @@ int paging_enable_for_car(const char *pdpt_name, const char *pt_name)
 
 static void *get_pdpt_addr(void)
 {
-	if (ENV_CACHE_AS_RAM)
+	if (preram_symbols_available())
 		return _pdpt;
 	return (void *)(uintptr_t)read_cr3();
 }

src/include/rules.h

@@ -274,8 +274,8 @@
 #define ENV_CACHE_AS_RAM		ENV_ROMSTAGE_OR_BEFORE
 /* No .data sections with execute-in-place from ROM.  */
 #define ENV_STAGE_HAS_DATA_SECTION	!ENV_CACHE_AS_RAM
-/* No .bss sections with execute-in-place from ROM.  */
+/* No .bss sections for stage with CAR teardown. */
-#define ENV_STAGE_HAS_BSS_SECTION	!ENV_CACHE_AS_RAM
+#define ENV_STAGE_HAS_BSS_SECTION	!(ENV_ROMSTAGE && CONFIG(CAR_GLOBAL_MIGRATION))
 #else
 /* Both .data and .bss, sometimes SRAM not DRAM. */
 #define ENV_STAGE_HAS_DATA_SECTION	1

src/lib/program.ld

@@ -125,7 +125,7 @@
 }
 #endif
 
-#if ENV_STAGE_HAS_BSS_SECTION
+#if ENV_STAGE_HAS_BSS_SECTION && !ENV_CACHE_AS_RAM
 .bss . : {
 	. = ALIGN(ARCH_POINTER_ALIGN_SIZE);
 	_bss = .;