efi/libstub: Measure into CC protocol if TCG2 protocol is absent

To accommodate confidential compute VMs that expose the simplified CC
measurement protocol instead of the full-blown TCG2 one, fall back to
the former if the latter does not exist.

The CC protocol was designed to be used in this manner, which is why the
types and prototypes have been kept the same where possible. So reuse
the existing code, and only deviate from the TCG2 code path where
needed.

Reviewed-by: Kuppuswamy Sathyanarayanan <[e-mail]>
Signed-off-by: Ard Biesheuvel <[e-mail]>

drivers/firmware/efi/libstub/efi-stub-helper.c

···
 	*load_options_size = load_option_unpacked.optional_data_size;
 }
 
-enum efistub_event {
+enum efistub_event_type {
 	EFISTUB_EVT_INITRD,
 	EFISTUB_EVT_LOAD_OPTIONS,
 	EFISTUB_EVT_COUNT,
···
 	},
 };
 
+static_assert(sizeof(efi_tcg2_event_t) == sizeof(efi_cc_event_t));
+
+union efistub_event {
+	efi_tcg2_event_t	tcg2_data;
+	efi_cc_event_t		cc_data;
+};
+
 struct efistub_measured_event {
-	efi_tcg2_event_t	event_data;
+	union efistub_event	event_data;
 	TCG_PCClientTaggedEvent tagged_event __packed;
 };
 
 static efi_status_t efi_measure_tagged_event(unsigned long load_addr,
 					     unsigned long load_size,
-					     enum efistub_event event)
+					     enum efistub_event_type event)
 {
+	union {
+		efi_status_t
+		(__efiapi *hash_log_extend_event)(void *, u64, efi_physical_addr_t,
+						  u64, const union efistub_event *);
+		struct { u32 hash_log_extend_event; } mixed_mode;
+	} method;
 	struct efistub_measured_event *evt;
 	int size = struct_size(evt, tagged_event.tagged_event_data,
 			       events[event].event_data_len);
 	efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
 	efi_tcg2_protocol_t *tcg2 = NULL;
+	union efistub_event ev;
 	efi_status_t status;
+	void *protocol;
 
 	efi_bs_call(locate_protocol, &tcg2_guid, NULL, (void **)&tcg2);
 	if (tcg2) {
-		status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size,
-				     (void **)&evt);
-		if (status != EFI_SUCCESS)
-			goto fail;
-
-		evt->event_data = (struct efi_tcg2_event){
+		ev.tcg2_data = (struct efi_tcg2_event){
 			.event_size			= size,
-			.event_header.header_size	= sizeof(evt->event_data.event_header),
+			.event_header.header_size	= sizeof(ev.tcg2_data.event_header),
 			.event_header.header_version	= EFI_TCG2_EVENT_HEADER_VERSION,
 			.event_header.pcr_index		= events[event].pcr_index,
 			.event_header.event_type	= EV_EVENT_TAG,
 		};
+		protocol = tcg2;
+		method.hash_log_extend_event =
+			(void *)efi_table_attr(tcg2, hash_log_extend_event);
+	} else {
+		efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID;
+		efi_cc_protocol_t *cc = NULL;
 
-		evt->tagged_event = (TCG_PCClientTaggedEvent){
-			.tagged_event_id		= events[event].event_id,
-			.tagged_event_data_size		= events[event].event_data_len,
+		efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc);
+		if (!cc)
+			return EFI_UNSUPPORTED;
+
+		ev.cc_data = (struct efi_cc_event){
+			.event_size			= size,
+			.event_header.header_size	= sizeof(ev.cc_data.event_header),
+			.event_header.header_version	= EFI_CC_EVENT_HEADER_VERSION,
+			.event_header.event_type	= EV_EVENT_TAG,
 		};
 
-		memcpy(evt->tagged_event.tagged_event_data, events[event].event_data,
-		       events[event].event_data_len);
-
-		status = efi_call_proto(tcg2, hash_log_extend_event, 0,
-					load_addr, load_size, &evt->event_data);
-		efi_bs_call(free_pool, evt);
-
+		status = efi_call_proto(cc, map_pcr_to_mr_index,
+					events[event].pcr_index,
+					&ev.cc_data.event_header.mr_index);
 		if (status != EFI_SUCCESS)
 			goto fail;
-		return EFI_SUCCESS;
+
+		protocol = cc;
+		method.hash_log_extend_event =
+			(void *)efi_table_attr(cc, hash_log_extend_event);
 	}
 
-	return EFI_UNSUPPORTED;
+	status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size, (void **)&evt);
+	if (status != EFI_SUCCESS)
+		goto fail;
+
+	*evt = (struct efistub_measured_event) {
+		.event_data			     = ev,
+		.tagged_event.tagged_event_id	     = events[event].event_id,
+		.tagged_event.tagged_event_data_size = events[event].event_data_len,
+	};
+
+	memcpy(evt->tagged_event.tagged_event_data, events[event].event_data,
+	       events[event].event_data_len);
+
+	status = efi_fn_call(&method, hash_log_extend_event, protocol, 0,
+			     load_addr, load_size, &evt->event_data);
+	efi_bs_call(free_pool, evt);
+
+	if (status == EFI_SUCCESS)
+		return EFI_SUCCESS;
+
 fail:
 	efi_warn("Failed to measure data for event %d: 0x%lx\n", event, status);
 	return status;