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>
diff --git a/src/arch/x86/init/romstage.ld b/src/arch/x86/init/romstage.ld
index 88c5657..f44185f 100644
--- a/src/arch/x86/init/romstage.ld
+++ b/src/arch/x86/init/romstage.ld
@@ -35,6 +35,10 @@
 		*(.rodata.*);
 		*(.rom.data.*);
 		. = ALIGN(16);
+		_car_migrate_start = .;
+		*(.car.migrate);
+		_car_migrate_end = .;
+		. = ALIGN(16);
 		_erom = .;
 	}
 
@@ -48,8 +52,16 @@
 
 	. = CONFIG_DCACHE_RAM_BASE;
 	.car.data . (NOLOAD) : {
+		_car_data_start = .;
 		*(.car.global_data);
+		/* The cbmem_console section comes last to take advantage of
+		 * a zero-sized array to hold the memconsole contents that
+		 * grows to a bound of CONFIG_CONSOLE_CAR_BUFFER_SIZE. However,
+		 * collisions within the cache-as-ram region cannot be
+		 * statically checked because the cache-as-ram region usage is
+		 * cpu/chipset dependent. */
 		*(.car.cbmem_console);
+		_car_data_end = .;
 	}
 
 	_bogus = ASSERT((SIZEOF(.car.data) <= CONFIG_DCACHE_RAM_SIZE), "Cache as RAM area is too full");
diff --git a/src/cpu/Makefile.inc b/src/cpu/Makefile.inc
index b48a803..8d93756 100644
--- a/src/cpu/Makefile.inc
+++ b/src/cpu/Makefile.inc
@@ -6,6 +6,7 @@
 subdirs-y += intel
 subdirs-y += samsung
 subdirs-y += via
+subdirs-y += x86
 
 ################################################################################
 ## Rules for building the microcode blob in CBFS
diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig
index c64a8e4..c10dd15 100644
--- a/src/cpu/x86/Kconfig
+++ b/src/cpu/x86/Kconfig
@@ -115,3 +115,12 @@
 	help
 	  This option informs the MTRR code to use the RdMem and WrMem fields
 	  in the fixed MTRR MSRs.
+
+config CAR_MIGRATION
+	def_bool n
+	depends on DYNAMIC_CBMEM || EARLY_CBMEM_INIT
+	help
+	  Migrate the cache-as-ram variables to CBMEM once CBMEM is set up
+	  in romstage. This option is only needed if one will be doing more
+	  work in romstage after the cache-as-ram is torn down aside from
+	  loading ramstage.
diff --git a/src/cpu/x86/Makefile.inc b/src/cpu/x86/Makefile.inc
new file mode 100644
index 0000000..fe8648c
--- /dev/null
+++ b/src/cpu/x86/Makefile.inc
@@ -0,0 +1 @@
+romstage-$(CONFIG_CAR_MIGRATION) += car.c
diff --git a/src/cpu/x86/car.c b/src/cpu/x86/car.c
new file mode 100644
index 0000000..31fc67c
--- /dev/null
+++ b/src/cpu/x86/car.c
@@ -0,0 +1,101 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2013 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <string.h>
+#include <stddef.h>
+#include <console/console.h>
+#include <cbmem.h>
+#include <cpu/x86/car.h>
+
+typedef void (* const car_migration_func_t)(void);
+
+extern car_migration_func_t _car_migrate_start;
+extern car_migration_func_t _car_migrate_end;
+
+extern char _car_data_start[];
+extern char _car_data_end[];
+
+/*
+ * The car_migrated global variable determines if the cache-as-ram space has
+ * been migrated to real RAM. It does this by asumming the following things:
+ *   1. cache-as-ram space is zero'd out once it is set up.
+ *   2. Either the cache-as-ram space is memory-backed after getting torn down
+ *      or the space returns 0xff's for each byte read.
+ * Based on these 2 attributes there is the ability to tell when the
+ * cache-as-ram region has been migrated.
+ */
+static int car_migrated CAR_GLOBAL;
+
+
+void *car_get_var_ptr(void *var)
+{
+	char *migrated_base;
+	int offset;
+	void * _car_start = &_car_data_start;
+	void * _car_end = &_car_data_end;
+
+	/* If the cache-as-ram has not been migrated return the pointer
+	 * passed in. */
+	if (!car_migrated)
+		return var;
+
+	if (var < _car_start || var >= _car_end) {
+		printk(BIOS_ERR,
+		       "Requesting CAR variable outside of CAR region: %p\n",
+		       var);
+		return var;
+	}
+
+	migrated_base = cbmem_find(CBMEM_ID_CAR_GLOBALS);
+
+	if (migrated_base == NULL) {
+		printk(BIOS_ERR, "CAR: Could not find migration base!\n");
+		return var;
+	}
+
+	offset = (char *)var - (char *)_car_start;
+
+	return &migrated_base[offset];
+}
+
+void car_migrate_variables(void)
+{
+	void *migrated_base;
+	car_migration_func_t *migrate_func;
+	size_t car_data_size = &_car_data_end[0] - &_car_data_start[0];
+
+	migrated_base = cbmem_add(CBMEM_ID_CAR_GLOBALS, car_data_size);
+
+	if (migrated_base == NULL) {
+		printk(BIOS_ERR, "Could not migrate CAR data!\n");
+		return;
+	}
+
+	memcpy(migrated_base, &_car_data_start[0], car_data_size);
+
+	/* Mark that the data has been moved. */
+	car_migrated = ~0;
+
+	/* Call all the migration functions. */
+	migrate_func = &_car_migrate_start;
+	while (migrate_func != &_car_migrate_end) {
+		(*migrate_func)();
+		migrate_func++;
+	}
+}
diff --git a/src/include/cbmem.h b/src/include/cbmem.h
index 67cb1cb..baec780 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 2d2af03..7b5cedf 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
diff --git a/src/lib/cbmem.c b/src/lib/cbmem.c
index e8200b6..3702da1 100644
--- a/src/lib/cbmem.c
+++ b/src/lib/cbmem.c
@@ -22,6 +22,7 @@
 #include <bootstate.h>
 #include <cbmem.h>
 #include <console/console.h>
+#include <cpu/x86/car.h>
 #if CONFIG_HAVE_ACPI_RESUME && !defined(__PRE_RAM__)
 #include <arch/acpi.h>
 #endif
@@ -228,6 +229,9 @@
 #ifndef __PRE_RAM__
 	cbmem_arch_init();
 #endif
+	/* Migrate cache-as-ram variables. */
+	car_migrate_variables();
+
 	return rv;
 }
 #endif
diff --git a/src/lib/cbmem_info.c b/src/lib/cbmem_info.c
index ad8c890..7031a70d 100644
--- a/src/lib/cbmem_info.c
+++ b/src/lib/cbmem_info.c
@@ -46,6 +46,7 @@
 	{ CBMEM_ID_RAMSTAGE_CACHE,	"RAMSTAGE $ " },
 	{ CBMEM_ID_ROOT,		"CBMEM ROOT " },
 	{ CBMEM_ID_VBOOT_HANDOFF,	"VBOOT      " },
+	{ CBMEM_ID_CAR_GLOBALS,		"CAR GLOBALS" },
 };
 
 void cbmem_print_entry(int n, u32 id, u64 base, u64 size)
diff --git a/src/lib/dynamic_cbmem.c b/src/lib/dynamic_cbmem.c
index 5c269a0..ba7760d 100644
--- a/src/lib/dynamic_cbmem.c
+++ b/src/lib/dynamic_cbmem.c
@@ -23,6 +23,7 @@
 #include <cbmem.h>
 #include <string.h>
 #include <stdlib.h>
+#include <cpu/x86/car.h>
 #if CONFIG_HAVE_ACPI_RESUME && !defined(__PRE_RAM__)
 #include <arch/acpi.h>
 #endif
@@ -182,12 +183,17 @@
 	       root, root->max_entries);
 
 	cbmem_arch_init();
+
+	/* Migrate cache-as-ram variables. */
+	car_migrate_variables();
 }
 
 static inline int cbmem_fail_recovery(void)
 {
 	cbmem_initialize_empty();
 	cbmem_handle_acpi_resume();
+	/* Migrate cache-as-ram variables. */
+	car_migrate_variables();
 	return 1;
 }
 
@@ -256,6 +262,9 @@
 
 	cbmem_arch_init();
 
+	/* Migrate cache-as-ram variables. */
+	car_migrate_variables();
+
 	/* Recovery successful. */
 	return 0;
 }