cr50: add unmarshaling of vendor commands and process 'enable_update'

The upcoming Cr50 firmware changes will require the AP to enable the
previously downloaded Cr50 firmware update(s).

A new vendor command (TPM2_CR50_SUB_CMD_TURN_UPDATE_ON) is used for
that. The command accepts one parameter - a timeout value in range of
0 to 1000 ms.

When processing the command the Cr50 checks if the alternative RO or
RW image(s) need to be enabled, and if so - enables them and returns
to the host the number of enabled headers.

If the vendor command requested a non-zero timeout, the Cr50 starts
a timer to trigger system reboot after the requested timeout expires.

The host acts on the number of enabled headers - if the number is
nonzero, the host prepares the device to be reset and waits for the
Cr50 to reboot the device after timeout expires.

This patch also adds more formal vendor command
marshaling/unmarshaling to make future additions easier.

BRANCH=gru,reef
BUG=b:35580805
TEST=with the actual user of this code in the next patch verified that
     the cr50 update is enabled as expected.

Change-Id: Ic76d384d637c0eeaad206e0a8242cbb8e2b19b37
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://review.coreboot.org/18945
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 25 insertions, 10 deletions

diff --git a/src/lib/tpm2_marshaling.c b/src/lib/tpm2_marshaling.c
index 6d4d622d91..52dac9c553 100644
--- a/src/lib/tpm2_marshaling.c
+++ b/src/lib/tpm2_marshaling.c
@@ -394,20 +394,16 @@ static void marshal_cr50_vendor_command(void **buffer, void *command_body,
 			size_t *buffer_space)
 {
 	uint16_t *sub_command;
-
-	/* Ensure at least the sub command can fit in the body and there's
-	   valid pointer. Could be reading past the buffer... */
-	if (command_body == NULL || *buffer_space < sizeof(uint16_t)) {
-		*buffer_space = 0;
-		return;
-	}
-
 	sub_command = command_body;
 
 	switch (*sub_command) {
 	case TPM2_CR50_SUB_CMD_NVMEM_ENABLE_COMMITS:
 		marshal_u16(buffer, *sub_command, buffer_space);
 		break;
+	case TPM2_CR50_SUB_CMD_TURN_UPDATE_ON:
+		marshal_u16(buffer, sub_command[0], buffer_space);
+		marshal_u16(buffer, sub_command[1], buffer_space);
+		break;
 	default:
 		/* Unsupported subcommand. */
 		printk(BIOS_WARNING, "Unsupported cr50 subcommand: 0x%04x\n",
@@ -596,6 +592,25 @@ static void unmarshal_nv_read(void **buffer, int *size,
 	*size = 0;
 }
 
+static void unmarshal_vendor_command(void **buffer, int *size,
+				     struct vendor_command_response *vcr)
+{
+	vcr->vc_subcommand = unmarshal_u16(buffer, size);
+
+	switch (vcr->vc_subcommand) {
+	case TPM2_CR50_SUB_CMD_NVMEM_ENABLE_COMMITS:
+		break;
+	case TPM2_CR50_SUB_CMD_TURN_UPDATE_ON:
+		vcr->num_restored_headers = unmarshal_u8(buffer, size);
+		break;
+	default:
+		printk(BIOS_ERR,
+		       "%s:%d - unsupported vendor command %#04x!\n",
+		       __func__, __LINE__, vcr->vc_subcommand);
+		break;
+	}
+}
+
 struct tpm2_response *tpm_unmarshal_response(TPM_CC command,
 					     void *response_body,
 					     size_t in_size)
@@ -648,8 +663,8 @@ struct tpm2_response *tpm_unmarshal_response(TPM_CC command,
 		break;
 
 	case TPM2_CR50_VENDOR_COMMAND:
-		/* Assume no other data returned for the time being. */
-		cr_size = 0;
+		unmarshal_vendor_command(&response_body, &cr_size,
+					 &tpm2_resp->vcr);
 		break;
 
 	default: