read EC Firmware hash from kernel secdata during board init

Cr50 reads EC Firmware hash from kernel secdata. This data shall be
used for EC-EFS (Early Firmware Selection) procedure.

BUG=chromium:1020578, b:148489182
BRANCH=cr50
TEST=none

Change-Id: Id8942b5b49dd5b0412d198a12ee0bf87fd59d47f
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1956159
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

6 files changed, 95 insertions, 2 deletions

diff --git a/board/cr50/ec_comm.h b/board/cr50/ec_comm.h
index 9e84a715e1..bec2deb57b 100644
--- a/board/cr50/ec_comm.h
+++ b/board/cr50/ec_comm.h
@@ -36,4 +36,8 @@ void ec_efs_reset(void);
 uint16_t ec_efs_set_boot_mode(const char *data, const uint8_t size);
 /* Verify the given hash data against the EC-FW hash from kernel secdata */
 uint16_t ec_efs_verify_hash(const char *hash_data, const uint8_t size);
+
+/* Re-load EC Hash code from TPM Kernel Secdata */
+void ec_efs_refresh(void);
+
 #endif /* __CROS_EC_COMM_H */
diff --git a/board/cr50/ec_efs.c b/board/cr50/ec_efs.c
index da5a31f019..677fb7d7f9 100644
--- a/board/cr50/ec_efs.c
+++ b/board/cr50/ec_efs.c
@@ -7,10 +7,13 @@
 #include "common.h"
 #include "console.h"
 #include "ec_comm.h"
+#include "crc8.h"
 #include "ec_commands.h"
 #include "hooks.h"
 #include "registers.h"
 #include "system.h"
+#include "tpm_nvmem.h"
+#include "tpm_nvmem_ops.h"
 #include "vboot.h"
 
 #ifdef CR50_DEV
@@ -48,6 +51,44 @@ static void set_boot_mode_(uint8_t mode_val)
 	GREG32(PMU, PWRDN_SCRATCH20) |= mode_val;
 }
 
+static int load_ec_hash_(uint8_t * const ec_hash)
+{
+	struct vb2_secdata_kernel secdata;
+	const uint8_t secdata_size = sizeof(struct vb2_secdata_kernel);
+	uint8_t size_to_crc;
+	uint8_t struct_size;
+	uint8_t crc;
+
+	if (read_tpm_nvmem(KERNEL_NV_INDEX, secdata_size,
+			   (void *)&secdata) != tpm_read_success)
+		return EC_ERROR_VBOOT_DATA_UNDERSIZED;
+
+	/*
+	 * Check struct version. CRC offset may be different with old struct
+	 * version
+	 */
+	if (secdata.struct_version < VB2_SECDATA_KERNEL_STRUCT_VERSION_MIN)
+		return EC_ERROR_VBOOT_DATA_INCOMPATIBLE;
+
+	/* Check struct size. */
+	struct_size = secdata.struct_size;
+	if (struct_size != secdata_size)
+		return EC_ERROR_VBOOT_DATA;
+
+	/* Check CRC */
+	size_to_crc = struct_size -
+		      offsetof(struct vb2_secdata_kernel, crc8) -
+		      sizeof(secdata.crc8);
+	crc = crc8((uint8_t *)&secdata.reserved0, size_to_crc);
+	if (crc != secdata.crc8)
+		return EC_ERROR_CRC;
+
+	/* Read hash and copy to hash */
+	memcpy(ec_hash, secdata.ec_hash, sizeof(secdata.ec_hash));
+
+	return EC_SUCCESS;
+}
+
 /*
  * Initialize EC-EFS context.
  */
@@ -66,7 +107,11 @@ static void ec_efs_init_(void)
 	else
 		ec_efs_reset();
 
-	/* TODO(crbug/1020578): Read Hash from Kernel NV Index */
+	/* Read an EC hash in kernel secdata (TPM kernel NV index). */
+	if (ec_efs_ctx.hash_is_loaded)
+		return;
+
+	ec_efs_refresh();
 }
 DECLARE_HOOK(HOOK_INIT, ec_efs_init_, HOOK_PRIO_DEFAULT);
 
@@ -74,3 +119,17 @@ void ec_efs_reset(void)
 {
 	set_boot_mode_(EC_EFS_BOOT_MODE_NORMAL);
 }
+
+void ec_efs_refresh(void)
+{
+	int rv;
+
+	rv = load_ec_hash_(ec_efs_ctx.hash);
+	if (rv == EC_SUCCESS) {
+		ec_efs_ctx.hash_is_loaded = 1;
+	} else {
+		ec_efs_ctx.hash_is_loaded = 0;
+		cprints(CC_SYSTEM, "load_ec_hash error: 0x%x\n", rv);
+	}
+	ec_efs_ctx.secdata_error_code = rv;
+}
diff --git a/board/cr50/tpm2/NVMem.c b/board/cr50/tpm2/NVMem.c
index e1a14b4536..052165d5b6 100644
--- a/board/cr50/tpm2/NVMem.c
+++ b/board/cr50/tpm2/NVMem.c
@@ -14,9 +14,12 @@
 
 #include "Platform.h"
 #include "PlatformData.h"
+#include "TPM_Types.h"
 #include "TpmError.h"
 #include "assert.h"
+#include "ec_comm.h"
 #include "nvmem.h"
+#include "tpm_nvmem.h"
 
 /* Local state */
 static struct {
@@ -188,3 +191,9 @@ void _plat__ClearNvAvail(void)
 	local_state.s_NvIsAvailable = FALSE;
 	return;
 }
+
+void _plat__NvInformIndexDataChanged(unsigned int handle)
+{
+	if (handle == (HR_NV_INDEX + KERNEL_NV_INDEX))
+		ec_efs_refresh();
+}
diff --git a/include/common.h b/include/common.h
index 99e9ad91c9..62f7d438d0 100644
--- a/include/common.h
+++ b/include/common.h
@@ -239,6 +239,8 @@ enum ec_error_list {
 	/* Verified boot data errors */
 	EC_ERROR_VBOOT_DATA = 0x1200,
 	EC_ERROR_VBOOT_DATA_VERIFY = 0x1201,
+	EC_ERROR_VBOOT_DATA_INCOMPATIBLE = 0x1202,
+	EC_ERROR_VBOOT_DATA_UNDERSIZED = 0x1203,
 
 	/* Module-internal error codes may use this range.   */
 	EC_ERROR_INTERNAL_FIRST = 0x10000,
diff --git a/include/tpm_nvmem.h b/include/tpm_nvmem.h
index 2508c9ae65..3315148323 100644
--- a/include/tpm_nvmem.h
+++ b/include/tpm_nvmem.h
@@ -8,6 +8,7 @@
 #define __CROS_EC_TPM_NVMEM_H
 
 #define FIRMWARE_NV_INDEX       0x1007
-#define FWMP_NV_INDEX		0x100a
+#define KERNEL_NV_INDEX         0x1008
+#define FWMP_NV_INDEX           0x100a
 
 #endif /* __CROS_EC_TPM_NVMEM_H */
diff --git a/include/vboot.h b/include/vboot.h
index 195db31a54..ba924508c7 100644
--- a/include/vboot.h
+++ b/include/vboot.h
@@ -72,6 +72,24 @@ enum ec_efs_boot_mode {
 	EC_EFS_BOOT_MODE_LIMIT            = 255,
 };
 
+/****************************************************************************
+ * This is quoted from 2secdata_struct.h in the directory,
+ * src/platform/vboot_reference/firmware/2lib/include/.
+ ****************************************************************************/
+
+/* Kernel secure storage space */
+#define VB2_SECDATA_KERNEL_STRUCT_VERSION_MIN  0x10
+#define VB2_SECDATA_KERNEL_UID          0x4752574c  /* 'LWRG' */
+struct vb2_secdata_kernel {
+	uint8_t struct_version;		/* top-half:major. bottom-half:minor. */
+	uint8_t struct_size;		/* Whole structure size */
+	uint8_t crc8;			/* CRC for everything below */
+	uint8_t reserved0;
+
+	uint32_t kernel_versions;	/* Kernel versions */
+	uint8_t ec_hash[SHA256_DIGEST_SIZE];
+} __packed;
+
 /**
  * Validate key contents.
  *