Invalidate hash if flash operation changes the hashed region

This prevents the EC from returning a stale hash.

BUG=chrome-os-partner:16668
BRANCH=link,snow
TEST=manual, with WP disabled

From EC console
- Boot system and wait a second
- hash --> prints valid hash
- flasherase 0x20000 0x1000
- hash --> invalid
- hash rw
- hash --> prints valid hash
- flashwrite 0x20000 0x1000
- hash --> invalid
- hash rw
- flasherase 0x38000 0x1000
- flashwrite 0x38000 0x1000
- hash --> still valid (since 0x38000 is outside the rw section)

From root shell
- ectool hash --> prints valid hash
- ectool flasherase 0x20000 0x1000
- ectool hash --> invalid
- ectool hash recalc RW
- ectool hash --> prints valid hash
- echo 'Making a hash of this' > /tmp/hashofthis
- ectool flashwrite 0x20000 /tmp/hashofthis
- ectool hash --> invalid
- ectool hash recalc RW
- ectool flasherase 0x38000 0x1000
- ectool flashwrite 0x38000 /tmp/hashofthis
- ectool hash --> still valid (since 0x38000 is outside the rw section)

Change-Id: Id915a504a7bc70b8b8c339b5ce55dc5bad5838fe
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39484
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/include/vboot_hash.h b/include/vboot_hash.h
new file mode 100644
index 0000000000..002282b346
--- /dev/null
+++ b/include/vboot_hash.h
@@ -0,0 +1,23 @@
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Verified boot hashing memory module for Chrome EC */
+
+#ifndef __CROS_EC_VBOOT_HASH_H
+#define __CROS_EC_VBOOT_HASH_H
+
+#include "common.h"
+
+/**
+ * Invalidate the hash if the hashed data overlaps the specified region.
+ *
+ * @param offset	Region start offset in flash
+ * @param size		Size of region in bytes
+ *
+ * @return non-zero if the region overlapped the hashed region.
+ */
+int vboot_hash_invalidate(int offset, int size);
+
+#endif  /* __CROS_EC_VBOOT_HASH_H */