vboot: Don't invalidate cached hash for EXEC_IN_RAM boards

Currently, a cached hash is invalidated on flash erase or write. This
causes the hash to be (unintentionally) equal to the one expected by the
AP after flashrom updates EC-RW directly on EXEC_IN_RAM devices.

This patch makes EC skip invalidation of the cached hash if the board
supports EXEC_IN_RAM. At the next AP reboot, AP will catch the hash
mismatch and triggers software sync to resolve the mismatch.

Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>

BUG=b:78285812,b:80143039
BRANCH=none
TEST=Verify EC-RO/RW versions are updated on a dogfood Akali as follows:
1. emerge-nami chromeos-firmware-nami to build chromeos-firmwareupdate
2. Replace bios.bin and ec.bin in chromeos-firmwareupdate with new images
4. Run 'chromeos-firmwareupdate -m autoupdate' on DUT
5. Run reboot command on AP

Change-Id: Ie5f80e4784814569c14d4cf2a03ddb9d1257cfd5
Reviewed-on: https://chromium-review.googlesource.com/1130552
Commit-Ready: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
(cherry picked from commit 65d6c6abbc2093067486e3e080adb4f24fc19acb)
Reviewed-on: https://chromium-review.googlesource.com/1135228
Commit-Queue: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 25 insertions, 22 deletions

diff --git a/common/flash.c b/common/flash.c
index 6746f178ef..8ae2be47e3 100644
--- a/common/flash.c
+++ b/common/flash.c
@@ -481,22 +481,35 @@ int flash_read(int offset, int size, char *data)
 #endif
 }
 
+static void flash_abort_or_invalidate_hash(int offset, int size)
+{
+#ifdef CONFIG_VBOOT_HASH
+	if (vboot_hash_in_progress()) {
+		/* Abort hash calculation when flash update is in progress. */
+		vboot_hash_abort();
+		return;
+	}
+
+#ifdef CONFIG_EXTERNAL_STORAGE
+	/*
+	 * If EC executes in RAM, we keep the current hash. On the next
+	 * hash check, AP will catch hash mismatch between the flash
+	 * copy and the RAM copy, then take necessary actions.
+	 */
+	return;
+#endif
+
+	/* If EC executes in place, we need to invalidate the cached hash. */
+	vboot_hash_invalidate(offset, size);
+#endif
+}
+
 int flash_write(int offset, int size, const char *data)
 {
 	if (!flash_range_ok(offset, size, CONFIG_FLASH_WRITE_SIZE))
 		return EC_ERROR_INVAL;  /* Invalid range */
 
-#ifdef CONFIG_VBOOT_HASH
-	/*
-	* Abort hash calculations when flashrom flash updates
-	* are in progress.Otherwise invalidate the pre-computed hash,
-	* since it's likely to change after flash write
-	*/
-	if (vboot_hash_in_progress())
-		vboot_hash_abort();
-	else
-		vboot_hash_invalidate(offset, size);
-#endif
+	flash_abort_or_invalidate_hash(offset, size);
 
 	return flash_physical_write(offset, size, data);
 }
@@ -508,17 +521,7 @@ int flash_erase(int offset, int size)
 		return EC_ERROR_INVAL;  /* Invalid range */
 #endif
 
-#ifdef CONFIG_VBOOT_HASH
-	/*
-	* Abort hash calculations when flashrom flash updates
-	* are in progress.Otherwise invalidate the pre-computed hash,
-	* since it's likely to be wrong after erase.
-	*/
-	if (vboot_hash_in_progress())
-		vboot_hash_abort();
-	else
-		vboot_hash_invalidate(offset, size);
-#endif
+	flash_abort_or_invalidate_hash(offset, size);
 
 	return flash_physical_erase(offset, size);
 }