x86: add cache-as-ram migration option

There are some boards that do a significant amount of
work after cache-as-ram is torn down but before ramstage
is loaded. For example, using vboot to verify the ramstage
is one such operation. However, there are pieces of code
that are executed that reference global variables that
are linked in the cache-as-ram region. If those variables
are referenced after cache-as-ram is torn down then the
values observed will most likely be incorrect.

Therefore provide a Kconfig option to select cache-as-ram
migration to memory using cbmem. This option is named
CAR_MIGRATION. When enabled, the address of cache-as-ram
variables may be obtained dynamically. Additionally,
when cache-as-ram migration occurs the cache-as-ram
data region for global variables is copied into cbmem.
There are also automatic callbacks for other modules
to perform their own migration, if necessary.

Change-Id: I2e77219647c2bd2b1aa845b262be3b2543f1fcb7
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/3232
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

2 files changed, 30 insertions, 0 deletions

diff --git a/src/include/cbmem.h b/src/include/cbmem.h
index 67cb1cb7e5..baec780156 100644
--- a/src/include/cbmem.h
+++ b/src/include/cbmem.h
@@ -69,6 +69,7 @@
 #define CBMEM_ID_RAMSTAGE_CACHE	0x9a3ca54e
 #define CBMEM_ID_ROOT		0xff4007ff
 #define CBMEM_ID_VBOOT_HANDOFF	0x780074f0
+#define CBMEM_ID_CAR_GLOBALS	0xcac4e6a3
 #define CBMEM_ID_NONE		0x00000000
 
 #ifndef __ASSEMBLER__
diff --git a/src/include/cpu/x86/car.h b/src/include/cpu/x86/car.h
index 2d2af03a37..7b5cedf213 100644
--- a/src/include/cpu/x86/car.h
+++ b/src/include/cpu/x86/car.h
@@ -28,4 +28,33 @@
 #define CAR_CBMEM
 #endif
 
+#if CONFIG_CAR_MIGRATION && defined(__PRE_RAM__)
+#define CAR_MIGRATE_ATTR __attribute__ ((used,section (".car.migrate")))
+
+/* Call migrate_fn_() when CAR globals are migrated. */
+#define CAR_MIGRATE(migrate_fn_) \
+	static void (* const migrate_fn_ ## _ptr)(void) CAR_MIGRATE_ATTR = \
+	migrate_fn_;
+
+/* Get the correct pointer for the CAR global variable. */
+void *car_get_var_ptr(void *var);
+
+/* Get and set a primitive type global variable. */
+#define car_get_var(var) \
+	*(typeof(var) *)car_get_var_ptr(&(var))
+#define car_set_var(var, val) \
+	do { car_get_var(var) = (val); } while(0)
+
+/* Migrate the CAR variables to memory. */
+void car_migrate_variables(void);
+
+#else
+#define CAR_MIGRATE(migrate_fn_)
+static inline void *car_get_var_ptr(void *var) { return var; }
+#define car_get_var(var) (var)
+#define car_set_var(var, val) do { (var) = (val); } while (0)
+static inline void car_migrate_variables(void) { }
+#endif
+
+
 #endif