arch/x86: Refactor CAR_GLOBAL quirk for FSP1.0

These platforms return to romstage from FSP only after
already having torn CAR down. A copy of the entire CAR
region is available and discoverable via HOB.

Previously, CBMEM console detected on-the-fly that CAR
migration had happened and relocated cbmem_console_p
accoringlin with car_sync_var(). However, if the CAR_GLOBAL
pointing to another object inside CAR is a relative offset
instead, we have a more generic solution that can be used
with timestamps code as well.

Change-Id: Ica877b47e68d56189e9d998b5630019d4328a419
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35140
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/arm/include/arch/early_variables.h

@@ -18,7 +18,9 @@
 
 static inline void *car_get_var_ptr(void *var) { return var; }
 #define car_get_var(var) (var)
-#define car_sync_var(var) (var)
 #define car_set_var(var, val) do { (var) = (val); } while (0)
 
+#define car_get_ptr car_get_var
+#define car_set_ptr car_set_var
+
 #endif

src/arch/arm64/include/arch/early_variables.h

@@ -18,7 +18,9 @@
 
 static inline void *car_get_var_ptr(void *var) { return var; }
 #define car_get_var(var) (var)
-#define car_sync_var(var) (var)
 #define car_set_var(var, val) do { (var) = (val); } while (0)
 
+#define car_get_ptr car_get_var
+#define car_set_ptr car_set_var
+
 #endif

src/arch/mips/include/arch/early_variables.h

@@ -19,7 +19,9 @@
 
 static inline void *car_get_var_ptr(void *var) { return var; }
 #define car_get_var(var) (var)
-#define car_sync_var(var) (var)
 #define car_set_var(var, val) { (var) = (val); }
 
+#define car_get_ptr car_get_var
+#define car_set_ptr car_set_var
+
 #endif /* __MIPS_ARCH_EARLY_VARIABLES_H */

src/arch/ppc64/include/arch/early_variables.h

@@ -19,8 +19,9 @@
 #define CAR_MIGRATE(migrate_fn_)
 static inline void *car_get_var_ptr(void *var) { return var; }
 #define car_get_var(var) (var)
-#define car_sync_var(var) (var)
-
 #define car_set_var(var, val) do { (var) = (val); } while (0)
 
+#define car_get_ptr car_get_var
+#define car_set_ptr car_set_var
+
 #endif

src/arch/riscv/include/arch/early_variables.h

@@ -21,7 +21,9 @@
 #define CAR_MIGRATE(migrate_fn_)
 static inline void *car_get_var_ptr(void *var) { return var; }
 #define car_get_var(var) (var)
-#define car_sync_var(var) (var)
 #define car_set_var(var, val) do { (var) = (val); } while (0)
 
+#define car_get_ptr car_get_var
+#define car_set_ptr car_set_var
+
 #endif

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

@@ -33,19 +33,25 @@ asm(".previous");
 /* Get the correct pointer for the CAR global variable. */
 void *car_get_var_ptr(void *var);
 
-/* Get and update a CAR_GLOBAL pointing elsewhere in car.global_data*/
-void *car_sync_var_ptr(void *var);
-
 /* Return 1 when currently running with globals in Cache-as-RAM, 0 otherwise. */
 int car_active(void);
 
 /* Get and set a primitive type global variable. */
 #define car_get_var(var) \
 	(*(typeof(var) *)car_get_var_ptr(&(var)))
-#define car_sync_var(var) \
-	(*(typeof(var) *)car_sync_var_ptr(&(var)))
 #define car_set_var(var, val)	car_get_var(var) = (val)
 
+/* Get and set a CAR_GLOBAL pointing elsewhere inside CAR. */
+#if !CONFIG(PLATFORM_USES_FSP1_0)
+#define car_get_ptr car_get_var
+#define car_set_ptr car_set_var
+#else
+void *car_get_reloc_ptr(void *var);
+void car_set_reloc_ptr(void *var, void *val);
+#define car_get_ptr(var) car_get_reloc_ptr(&(var))
+#define car_set_ptr(var, val) car_set_reloc_ptr(&(var), (val))
+#endif
+
 static inline size_t car_data_size(void)
 {
 	size_t car_size = _car_relocatable_data_size;
@@ -66,8 +72,9 @@ static inline size_t car_object_offset(void *ptr)
 
 #define CAR_GLOBAL
 #define car_get_var(var) (var)
-#define car_sync_var(var) (var)
 #define car_set_var(var, val)	(var) = (val)
+#define car_get_ptr car_get_var
+#define car_set_ptr car_set_var
 
 static inline void *car_get_var_ptr(void *var)
 {

src/cpu/x86/car.c

@@ -77,42 +77,37 @@ void *car_get_var_ptr(void *var)
 	return &migrated_base[offset];
 }
 
+#if CONFIG(PLATFORM_USES_FSP1_0)
 /*
- * Update a CAR_GLOBAL variable var, originally pointing to CAR region,
- * with the address in migrated CAR region in DRAM.
+ * When a CAR_GLOBAL points to target object inside CAR, use relative
+ * addressing. Such CAR_GLOBAL has to be expicitly accessed using
+ * car_set_reloc_ptr() and car_get_reloc_ptr() as the stored value is now
+ * an offset instead of the absolute address (pointer) of the target.
+ *
+ * This way discovery of objects that are not CAR_GLOBALs themselves,
+ * remain discoverable after CAR migration has implicitly happened.
  */
-void *car_sync_var_ptr(void *var)
+void car_set_reloc_ptr(void *var, void *val)
 {
-	void **mig_var = car_get_var_ptr(var);
-	void *_car_start = _car_relocatable_data_start;
-	void *_car_end = _car_relocatable_data_end;
+	uintptr_t *offset = car_get_var_ptr(var);
+	*offset = 0;
 
-	/* Not moved or migrated yet. */
-	if (mig_var == var)
-		return mig_var;
-
-	/*
-	 * Migrate the cbmem console pointer for FSP 1.0 platforms. Otherwise,
-	 * keep console buffer in CAR until cbmemc_reinit() moves it.
-	 */
-	if (*mig_var == _preram_cbmem_console) {
-		if (CONFIG(PLATFORM_USES_FSP1_0))
-			*mig_var += (char *)mig_var - (char *)var;
-		return mig_var;
-	}
-
-	/* It's already pointing outside car.global_data. */
-	if (*mig_var < _car_start || *mig_var > _car_end)
-		return mig_var;
-
-	/* Move the pointer by the same amount the variable storing it was
-	 * moved by.
-	 */
-	*mig_var += (char *)mig_var - (char *)var;
-
-	return mig_var;
+	if (val)
+		*offset = (uintptr_t)offset - (uintptr_t)val;
 }
 
+void *car_get_reloc_ptr(void *var)
+{
+	uintptr_t *offset = car_get_var_ptr(var);
+	void *val = NULL;
+
+	if (*offset)
+		val = (void *)((uintptr_t)offset - *offset);
+
+	return val;
+}
+#endif
+
 int car_active(void)
 {
 	return !car_migrated;

src/lib/cbmem_console.c

@@ -73,12 +73,12 @@ static u8 static_console[STATIC_CONSOLE_SIZE];
 
 static struct cbmem_console *current_console(void)
 {
-	return car_sync_var(cbmem_console_p);
+	return car_get_ptr(cbmem_console_p);
 }
 
 static void current_console_set(struct cbmem_console *new_console_p)
 {
-	car_set_var(cbmem_console_p, new_console_p);
+	car_set_ptr(cbmem_console_p, new_console_p);
 }
 
 static int buffer_valid(struct cbmem_console *cbm_cons_p, u32 total_space)