chromeos: Make vbnv_flash driver safe for CAR usage

This modifies the vbnv_flash driver to make it safe for use
in cache-as-ram by handling the global variables safely.

To make this cleaner all of the variables were moved into
one structure and referenced from there.

BUG=chrome-os-partner:47915
BRANCH=glados
TEST=build and boot on chell using following patches to
test backup and restore of vbnv_cmos into flash

Change-Id: I3a17fa51cfd754455502ac2e5f181dae35967f2a
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 48876561fa4fb61e1ec8f92596c5610d97135201
Original-Change-Id: Id9fda8467edcc55e5ed760ddab197ab97d1f3d25
Original-Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/324121
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13599
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/vendorcode/google/chromeos/vbnv_flash.c b/src/vendorcode/google/chromeos/vbnv_flash.c
index ea5d9f3..88f39b0 100644
--- a/src/vendorcode/google/chromeos/vbnv_flash.c
+++ b/src/vendorcode/google/chromeos/vbnv_flash.c
@@ -11,10 +11,9 @@
  * 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.
- *
- * TODO: Make this CAR-friendly in case we use it on x86 some day.
  */
 
+#include <arch/early_variables.h>
 #include <assert.h>
 #include <console/console.h>
 #include <spi_flash.h>
@@ -27,20 +26,26 @@
 
 #define BLOB_SIZE VB2_NVDATA_SIZE
 
-/* FMAP descriptor of the NVRAM area */
-static struct region_device nvram_region;
+struct vbnv_flash_ctx {
+	/* VBNV flash is initialized */
+	int initialized;
 
-/* offset of the current nvdata in SPI flash */
-static int blob_offset = -1;
+	/* Offset of the current nvdata in SPI flash */
+	int blob_offset;
 
-/* Offset of the topmost nvdata blob in SPI flash */
-static int top_offset;
+	/* Offset of the topmost nvdata blob in SPI flash */
+	int top_offset;
 
-/* cache of the current nvdata */
-static uint8_t cache[BLOB_SIZE];
+	/* SPI flash handler used when saving data */
+	struct spi_flash *flash;
 
-/* spi_flash struct used when saving data */
-static struct spi_flash *spi_flash = NULL;
+	/* FMAP descriptor of the NVRAM area */
+	struct region_device region;
+
+	/* Cache of the current nvdata */
+	uint8_t cache[BLOB_SIZE];
+};
+static struct vbnv_flash_ctx vbnv_flash CAR_GLOBAL;
 
 /*
  * This code assumes that flash is erased to 1-bits, and write operations can
@@ -57,20 +62,16 @@
 	return (current & new) == new;
 }
 
-static inline int is_initialized(void)
-{
-	return blob_offset >= 0;
-}
-
 static int init_vbnv(void)
 {
+	struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
 	uint8_t buf[BLOB_SIZE];
 	uint8_t empty_blob[BLOB_SIZE];
 	int offset;
 	int i;
 
-	if (vboot_named_region_device("RW_NVRAM", &nvram_region) ||
-	    region_device_sz(&nvram_region) < BLOB_SIZE) {
+	if (vboot_named_region_device("RW_NVRAM", &ctx->region) ||
+	    region_device_sz(&ctx->region) < BLOB_SIZE) {
 		printk(BIOS_ERR, "%s: failed to locate NVRAM\n", __func__);
 		return 1;
 	}
@@ -80,7 +81,7 @@
 		empty_blob[i] = erase_value();
 
 	offset = 0;
-	top_offset = region_device_sz(&nvram_region) - BLOB_SIZE;
+	ctx->top_offset = region_device_sz(&ctx->region) - BLOB_SIZE;
 
 	/*
 	 * after the loop, offset is supposed to point the blob right before
@@ -88,8 +89,8 @@
 	 * empty blob, or the base of the region if the nvram has never been
 	 * used.
 	 */
-	for (i = 0; i <= top_offset; i += BLOB_SIZE) {
-		if (rdev_readat(&nvram_region, buf, i, BLOB_SIZE) < 0) {
+	for (i = 0; i <= ctx->top_offset; i += BLOB_SIZE) {
+		if (rdev_readat(&ctx->region, buf, i, BLOB_SIZE) < 0) {
 			printk(BIOS_ERR, "failed to read nvdata\n");
 			return 1;
 		}
@@ -99,12 +100,13 @@
 	}
 
 	/* reread the nvdata and write it to the cache */
-	if (rdev_readat(&nvram_region, cache, offset, BLOB_SIZE) < 0) {
+	if (rdev_readat(&ctx->region, ctx->cache, offset, BLOB_SIZE) < 0) {
 		printk(BIOS_ERR, "failed to read nvdata\n");
 		return 1;
 	}
 
-	blob_offset = offset;
+	ctx->blob_offset = offset;
+	ctx->initialized = 1;
 
 	return 0;
 }
@@ -122,15 +124,19 @@
 	 *
 	 * TODO: Check by calling can_erase implemented by each spi flash driver
 	 */
-	assert(!(region_device_offset(&nvram_region) % spi_flash->sector_size));
-	assert(!(region_device_sz(&nvram_region) % spi_flash->sector_size));
+	struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+
+	assert(!(region_device_offset(&ctx->region) % ctx->flash->sector_size));
+	assert(!(region_device_sz(&ctx->region) % ctx->flash->sector_size));
 }
 
 static int vbnv_flash_probe(void)
 {
-	if (!spi_flash) {
-		spi_flash = spi_flash_probe(CONFIG_BOOT_MEDIA_SPI_BUS, 0);
-		if (!spi_flash) {
+	struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+
+	if (!ctx->flash) {
+		ctx->flash = spi_flash_probe(CONFIG_BOOT_MEDIA_SPI_BUS, 0);
+		if (!ctx->flash) {
 			printk(BIOS_ERR, "failed to probe spi flash\n");
 			return 1;
 		}
@@ -140,16 +146,25 @@
 		 */
 		vbnv_is_erasable();
 	}
+
+	/*
+	 * Handle the case where spi_flash_probe returns a CAR_GLOBAL
+	 * in early execution on x86 but then later is moved to RAM.
+	 */
+	ctx->flash = car_get_var_ptr(ctx->flash);
+
 	return 0;
 }
 
 static int erase_nvram(void)
 {
+	struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+
 	if (vbnv_flash_probe())
 		return 1;
 
-	if (spi_flash->erase(spi_flash, region_device_offset(&nvram_region),
-			     region_device_sz(&nvram_region))) {
+	if (ctx->flash->erase(ctx->flash, region_device_offset(&ctx->region),
+			      region_device_sz(&ctx->region))) {
 		printk(BIOS_ERR, "failed to erase nvram\n");
 		return 1;
 	}
@@ -160,33 +175,37 @@
 
 void read_vbnv_flash(uint8_t *vbnv_copy)
 {
-	if (!is_initialized())
+	struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+
+	if (!ctx->initialized)
 		if (init_vbnv())
 			return;  /* error */
-	memcpy(vbnv_copy, cache, BLOB_SIZE);
+
+	memcpy(vbnv_copy, ctx->cache, BLOB_SIZE);
 }
 
 void save_vbnv_flash(const uint8_t *vbnv_copy)
 {
+	struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
 	int new_offset;
 	int i;
 
-	if (!is_initialized())
+	if (!ctx->initialized)
 		if (init_vbnv())
 			return;  /* error */
 
 	/* Bail out if there have been no changes. */
-	if (!memcmp(vbnv_copy, cache, BLOB_SIZE))
+	if (!memcmp(vbnv_copy, ctx->cache, BLOB_SIZE))
 		return;
 
-	new_offset = blob_offset;
+	new_offset = ctx->blob_offset;
 
 	/* See if we can overwrite the current blob with the new one */
 	for (i = 0; i < BLOB_SIZE; i++) {
-		if (!can_overwrite(cache[i], vbnv_copy[i])) {
+		if (!can_overwrite(ctx->cache[i], vbnv_copy[i])) {
 			/* unable to overwrite. need to use the next blob */
 			new_offset += BLOB_SIZE;
-			if (new_offset > top_offset) {
+			if (new_offset > ctx->top_offset) {
 				if (erase_nvram())
 					return;  /* error */
 				new_offset = 0;
@@ -196,12 +215,12 @@
 	}
 
 	if (!vbnv_flash_probe() &&
-	    !spi_flash->write(spi_flash,
-			      region_device_offset(&nvram_region) + new_offset,
-			      BLOB_SIZE, vbnv_copy)) {
+	    !ctx->flash->write(ctx->flash,
+			       region_device_offset(&ctx->region) + new_offset,
+			       BLOB_SIZE, vbnv_copy)) {
 		/* write was successful. safely move pointer forward */
-		blob_offset = new_offset;
-		memcpy(cache, vbnv_copy, BLOB_SIZE);
+		ctx->blob_offset = new_offset;
+		memcpy(ctx->cache, vbnv_copy, BLOB_SIZE);
 	} else {
 		printk(BIOS_ERR, "failed to save nvdata\n");
 	}