efi/libstub: Use TPM event typedefs from the TCG PC Client spec

Our efi_tcg2_tagged_event is not defined in the EFI spec, but it is not
a local invention either: it was taken from the TCG PC Client spec,
where it is called TCG_PCClientTaggedEvent.

Note that this spec also contains some guidance on how to populate it,
which is not being followed closely at the moment; it claims that the
event size should cover the TCG_PCClientTaggedEvent and its payload
only, but it currently covers the preceding efi_tcg2_event too.

However, this directly contradicts the TCG EFI protocol specification,
which states very clearly that the event size should cover the entire
data structure, including the leading efi_tcg2_event_t struct.

So rename the struct and document its provenance, but retain the
existing logic to populate the size field.

Link: https://lore.kernel.org/all/20240308085754.476197-8-ardb+git@google.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

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

@@ -11,6 +11,7 @@
 
 #include <linux/efi.h>
 #include <linux/kernel.h>
+#include <linux/overflow.h>
 #include <asm/efi.h>
 #include <asm/setup.h>
 
@@ -219,23 +220,24 @@ static const struct {
 	},
 };
 
+struct efistub_measured_event {
+	efi_tcg2_event_t	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)
 {
+	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;
 	efi_status_t status;
 
 	efi_bs_call(locate_protocol, &tcg2_guid, NULL, (void **)&tcg2);
 	if (tcg2) {
-		struct efi_measured_event {
-			efi_tcg2_event_t	event_data;
-			efi_tcg2_tagged_event_t tagged_event;
-			u8			tagged_event_data[];
-		} *evt;
-		int size = sizeof(*evt) + events[event].event_data_len;
-
 		status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size,
 				     (void **)&evt);
 		if (status != EFI_SUCCESS)
@@ -249,12 +251,12 @@ static efi_status_t efi_measure_tagged_event(unsigned long load_addr,
 			.event_header.event_type	= EV_EVENT_TAG,
 		};
 
-		evt->tagged_event = (struct efi_tcg2_tagged_event){
+		evt->tagged_event = (TCG_PCClientTaggedEvent){
 			.tagged_event_id		= events[event].event_id,
 			.tagged_event_data_size		= events[event].event_data_len,
 		};
 
-		memcpy(evt->tagged_event_data, events[event].event_data,
+		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,

drivers/firmware/efi/libstub/efistub.h

@@ -843,14 +843,14 @@ struct efi_tcg2_event {
 	/* u8[] event follows here */
 } __packed;
 
-struct efi_tcg2_tagged_event {
-	u32 tagged_event_id;
-	u32 tagged_event_data_size;
-	/* u8  tagged event data follows here */
-} __packed;
+/* from TCG PC Client Platform Firmware Profile Specification */
+typedef struct tdTCG_PCClientTaggedEvent {
+	u32	tagged_event_id;
+	u32	tagged_event_data_size;
+	u8	tagged_event_data[];
+} TCG_PCClientTaggedEvent;
 
 typedef struct efi_tcg2_event efi_tcg2_event_t;
-typedef struct efi_tcg2_tagged_event efi_tcg2_tagged_event_t;
 typedef union efi_tcg2_protocol efi_tcg2_protocol_t;
 
 union efi_tcg2_protocol {