New patch to review for coreboot: google/chromeec: implement vboot_(save|retrieve)_hash API

[Patrick Georgi]

Patrick Georgi ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/13577

-gerrit

commit c80665a73a8fa35d6dc1757b08835ade9313aacf
Author: Aaron Durbin 
Date:   Fri Jan 22 14:42:54 2016 -0600

google/chromeec: implement vboot_(save|retrieve)_hash API

For x86 systems which resume through the reset vector one needs to
    ensure the the RW slot taken at resume time matches the one at
    boot time. To that end, allow Chrome OS EC to supply the plumbing
    to vboot for storing and retrieving the RW slots' hash digest
    using the vstore backend.

BUG=chrome-os-partner:46049
    BRANCH=glados
    TEST=Suspended and resumed on chell. Also, tested with an EC build
         which returns a bad hash to ensure that is properly caught.

Change-Id: Ib056f7e6b3386447ed1ff95c740ef5b4544f9049
    Signed-off-by: Patrick Georgi 
    Original-Commit-Id: 9c78546b1d6298a4c397a587c564df6d9d097e75
    Original-Change-Id: I86c96a4092deab2dfa51b3043b9dba16b6a4c201
    Original-Signed-off-by: Aaron Durbin 
    Original-Reviewed-on: https://chromium-review.googlesource.com/323502
    Original-Reviewed-by: Patrick Georgi 
    Original-Reviewed-by: Duncan Laurie 
---
 src/ec/google/chromeec/Makefile.inc    |  5 +++
 src/ec/google/chromeec/vboot_storage.c | 62 ++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/src/ec/google/chromeec/Makefile.inc b/src/ec/google/chromeec/Makefile.inc
index 59758ca..ad9de9e 100644
--- a/src/ec/google/chromeec/Makefile.inc
+++ b/src/ec/google/chromeec/Makefile.inc
@@ -21,4 +21,9 @@ verstage-$(CONFIG_EC_GOOGLE_CHROMEEC_LPC) += ec_lpc.c
 verstage-$(CONFIG_EC_GOOGLE_CHROMEEC_MEC) += ec_mec.c
 verstage-$(CONFIG_EC_GOOGLE_CHROMEEC_SPI) += ec_spi.c

+ramstage-$(CONFIG_VBOOT_VERIFY_FIRMWARE) += vboot_storage.c
+smm-$(CONFIG_VBOOT_VERIFY_FIRMWARE) += vboot_storage.c
+romstage-$(CONFIG_VBOOT_VERIFY_FIRMWARE) += vboot_storage.c
+verstage-$(CONFIG_VBOOT_VERIFY_FIRMWARE) += vboot_storage.c
+
 endif
diff --git a/src/ec/google/chromeec/vboot_storage.c b/src/ec/google/chromeec/vboot_storage.c
new file mode 100644
index 0000000..f47c2f1
--- /dev/null
+++ b/src/ec/google/chromeec/vboot_storage.c
@@ -0,0 +1,62 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2016 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.
+ */
+
+#include <assert.h>
+#include <console/console.h>
+#include <ec/google/chromeec/ec.h>
+#include <vendorcode/google/chromeos/chromeos.h>
+
+#define VBOOT_HASH_VSLOT 0
+#define VBOOT_HASH_VSLOT_MASK (1 << (VBOOT_HASH_VSLOT))
+
+int vboot_save_hash(void *digest, size_t digest_size)
+{
+	const int slot = VBOOT_HASH_VSLOT;
+	uint32_t lock_status;
+	int num_slots;
+
+	/* Ensure the digests being saved match the EC's slot size. */
+	assert(digest_size == EC_VSTORE_SLOT_SIZE);
+
+	if (google_chromeec_vstore_write(slot, digest, digest_size))
+		return -1;
+
+	/* Assert the slot is locked on successful write. */
+	num_slots = google_chromeec_vstore_info(&lock_status);
+
+	/* Normalize to be 0 based. If num_slots returned 0 then it'll be -1. */
+	num_slots--;
+
+	if (num_slots < slot) {
+		printk(BIOS_ERR, "Not enough vstore slots for vboot hash: %d\n",
+			num_slots + 1);
+		return -1;
+	}
+
+	if ((lock_status & VBOOT_HASH_VSLOT_MASK) == 0) {
+		printk(BIOS_ERR, "Vstore slot not locked after write.\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+int vboot_retrieve_hash(void *digest, size_t digest_size)
+{
+	/* Ensure the digests being saved match the EC's slot size. */
+	assert(digest_size == EC_VSTORE_SLOT_SIZE);
+
+	return google_chromeec_vstore_read(VBOOT_HASH_VSLOT, digest);
+}