ec: Add temporary secure storage for the host during boot

This adds a temporary secure storage interface for the EC to be able
to store small amounts of data from the host that is locked until the
chipset resets.  This is used by pre-memory verified boot on x86 systems
where we need to know which RW slot to boot and what the hash is to
ensure that we can resume from S3 safely.

BUG=chrome-os-partner:46049
BRANCH=none
TEST=tested on glados and samus

Change-Id: I5fa91046437479bcae69a8fca4c989b0ef554bbf
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/315222
Commit-Ready: Aaron Durbin <adurbin@chromium.org>
Tested-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Shawn N <shawnn@chromium.org>

1 files changed, 127 insertions, 0 deletions

diff --git a/common/vstore.c b/common/vstore.c
new file mode 100644
index 0000000000..a2d81ba9a5
--- /dev/null
+++ b/common/vstore.c
@@ -0,0 +1,127 @@
+/* Copyright 2015 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.
+ */
+
+/*
+ * Temporary secure storage commands for use by the host for verified boot
+ * related activities such as storing the hash of verified firmware for use
+ * in suspend/resume.
+ *
+ * There are a configurable number of vstore slots, with all slots having
+ * the same size of EC_VSTORE_SLOT_SIZE (64 bytes).
+ *
+ * Slots can be written once per AP power-on and will then be locked and
+ * cannot be written again until it is cleared in the CHIPSET_SHUTDOWN
+ * or CHIPSET_RESET hooks.
+ */
+
+#include "common.h"
+#include "hooks.h"
+#include "host_command.h"
+#include "system.h"
+#include "util.h"
+
+#define VSTORE_SYSJUMP_TAG  0x5653 /* "VS" */
+#define VSTORE_HOOK_VERSION 1
+
+struct vstore_slot {
+	uint8_t locked;
+	uint8_t data[EC_VSTORE_SLOT_SIZE];
+};
+
+static struct vstore_slot vstore_slots[CONFIG_VSTORE_SLOT_COUNT];
+static const int vstore_size =
+		sizeof(struct vstore_slot) * CONFIG_VSTORE_SLOT_COUNT;
+BUILD_ASSERT(ARRAY_SIZE(vstore_slots) <= EC_VSTORE_SLOT_MAX);
+
+/*
+ * vstore_info - Get slot count and mask of locked slots.
+ */
+static int vstore_info(struct host_cmd_handler_args *args)
+{
+	struct ec_response_vstore_info *r = args->response;
+	int i;
+
+	r->slot_count = CONFIG_VSTORE_SLOT_COUNT;
+	r->slot_locked = 0;
+	for (i = 0; i < CONFIG_VSTORE_SLOT_COUNT; i++)
+		if (vstore_slots[i].locked)
+			r->slot_locked |= 1 << i;
+
+	args->response_size = sizeof(*r);
+
+	return EC_RES_SUCCESS;
+}
+DECLARE_HOST_COMMAND(EC_CMD_VSTORE_INFO, vstore_info, EC_VER_MASK(0));
+
+/*
+ * vstore_read - Read slot from temporary secure storage.
+ *
+ * Response is EC_VSTORE_SLOT_SIZE bytes of data.
+ */
+static int vstore_read(struct host_cmd_handler_args *args)
+{
+	const struct ec_params_vstore_read *p = args->params;
+	struct ec_response_vstore_read *r = args->response;
+
+	if (p->slot >= CONFIG_VSTORE_SLOT_COUNT)
+		return EC_RES_INVALID_PARAM;
+
+	memcpy(r->data, vstore_slots[p->slot].data, EC_VSTORE_SLOT_SIZE);
+
+	args->response_size = sizeof(*r);
+
+	return EC_RES_SUCCESS;
+}
+DECLARE_HOST_COMMAND(EC_CMD_VSTORE_READ, vstore_read, EC_VER_MASK(0));
+
+/*
+ * vstore_write - Write temporary secure storage slot and lock it.
+ */
+static int vstore_write(struct host_cmd_handler_args *args)
+{
+	const struct ec_params_vstore_write *p = args->params;
+	struct vstore_slot *slot;
+
+	if (p->slot >= CONFIG_VSTORE_SLOT_COUNT)
+		return EC_RES_INVALID_PARAM;
+	slot = &vstore_slots[p->slot];
+
+	if (slot->locked)
+		return EC_RES_ACCESS_DENIED;
+	slot->locked = 1;
+	memcpy(slot->data, p->data, EC_VSTORE_SLOT_SIZE);
+
+	return EC_RES_SUCCESS;
+}
+DECLARE_HOST_COMMAND(EC_CMD_VSTORE_WRITE, vstore_write, EC_VER_MASK(0));
+
+static void vstore_clear_lock(void)
+{
+	int i;
+
+	for (i = 0; i < CONFIG_VSTORE_SLOT_COUNT; i++)
+		vstore_slots[i].locked = 0;
+}
+DECLARE_HOOK(HOOK_CHIPSET_RESET, vstore_clear_lock, HOOK_PRIO_DEFAULT);
+
+static void vstore_preserve_state(void)
+{
+	system_add_jump_tag(VSTORE_SYSJUMP_TAG, VSTORE_HOOK_VERSION,
+			    vstore_size, vstore_slots);
+}
+DECLARE_HOOK(HOOK_SYSJUMP, vstore_preserve_state, HOOK_PRIO_DEFAULT);
+
+static void vstore_init(void)
+{
+	const struct vstore_slot *prev;
+	int version, size;
+
+	prev = (const struct vstore_slot *)system_get_jump_tag(
+		VSTORE_SYSJUMP_TAG, &version, &size);
+
+	if (prev && version == VSTORE_HOOK_VERSION && size == vstore_size)
+		memcpy(vstore_slots, prev, vstore_size);
+}
+DECLARE_HOOK(HOOK_INIT, vstore_init, HOOK_PRIO_DEFAULT);