efi/libstub: refactor the initrd measuring functions

Currently, from the efi-stub, we are only measuring the loaded initrd,
using the TCG2 measured boot protocols.  A following patch is
introducing measurements of additional components, such as the kernel
command line. On top of that, we will shortly have to support other
types of measured boot that don't expose the TCG2 protocols.

So let's prepare for that, by rejigging the efi_measure_initrd() routine
into something that we should be able to reuse for measuring other
assets, and which can be extended later to support other measured boot
protocols.
Co-developed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

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

@@ -334,6 +334,79 @@ void efi_apply_loadoptions_quirk(const void **load_options, u32 *load_options_si
 	*load_options_size = load_option_unpacked.optional_data_size;
 }
 
+enum efistub_event {
+	EFISTUB_EVT_INITRD,
+	EFISTUB_EVT_COUNT,
+};
+
+#define STR_WITH_SIZE(s)	sizeof(s), s
+
+static const struct {
+	u32		pcr_index;
+	u32		event_id;
+	u32		event_data_len;
+	u8		event_data[52];
+} events[] = {
+	[EFISTUB_EVT_INITRD] = {
+		9,
+		INITRD_EVENT_TAG_ID,
+		STR_WITH_SIZE("Linux initrd")
+	},
+};
+
+static efi_status_t efi_measure_tagged_event(unsigned long load_addr,
+					     unsigned long load_size,
+					     enum efistub_event event)
+{
+	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)
+			goto fail;
+
+		evt->event_data = (struct efi_tcg2_event){
+			.event_size			= size,
+			.event_header.header_size	= sizeof(evt->event_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,
+		};
+
+		evt->tagged_event = (struct efi_tcg2_tagged_event){
+			.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,
+		       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);
+
+		if (status != EFI_SUCCESS)
+			goto fail;
+		return EFI_SUCCESS;
+	}
+
+	return EFI_UNSUPPORTED;
+fail:
+	efi_warn("Failed to measure data for event %d: 0x%lx\n", event, status);
+	return status;
+}
+
 /*
  * Convert the unicode UEFI command line to ASCII to pass to kernel.
  * Size of memory allocated return in *cmd_line_len.
@@ -607,47 +680,6 @@ efi_status_t efi_load_initrd_cmdline(efi_loaded_image_t *image,
 				    &initrd->base, &initrd->size);
 }
 
-static const struct {
-	efi_tcg2_event_t	event_data;
-	efi_tcg2_tagged_event_t tagged_event;
-	u8			tagged_event_data[];
-} initrd_tcg2_event = {
-	{
-		sizeof(initrd_tcg2_event) + sizeof("Linux initrd"),
-		{
-			sizeof(initrd_tcg2_event.event_data.event_header),
-			EFI_TCG2_EVENT_HEADER_VERSION,
-			9,
-			EV_EVENT_TAG,
-		},
-	},
-	{
-		INITRD_EVENT_TAG_ID,
-		sizeof("Linux initrd"),
-	},
-	{ "Linux initrd" },
-};
-
-static void efi_measure_initrd(unsigned long load_addr, unsigned long load_size)
-{
-	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) {
-		status = efi_call_proto(tcg2, hash_log_extend_event,
-					0, load_addr, load_size,
-					&initrd_tcg2_event.event_data);
-		if (status != EFI_SUCCESS)
-			efi_warn("Failed to measure initrd data: 0x%lx\n",
-				 status);
-		else
-			efi_info("Measured initrd data into PCR %d\n",
-				 initrd_tcg2_event.event_data.event_header.pcr_index);
-	}
-}
-
 /**
  * efi_load_initrd() - Load initial RAM disk
  * @image:	EFI loaded image protocol
@@ -671,8 +703,10 @@ efi_status_t efi_load_initrd(efi_loaded_image_t *image,
 	status = efi_load_initrd_dev_path(&initrd, hard_limit);
 	if (status == EFI_SUCCESS) {
 		efi_info("Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path\n");
-		if (initrd.size > 0)
-			efi_measure_initrd(initrd.base, initrd.size);
+		if (initrd.size > 0 &&
+		    efi_measure_tagged_event(initrd.base, initrd.size,
+					     EFISTUB_EVT_INITRD) == EFI_SUCCESS)
+			efi_info("Measured initrd data into PCR 9\n");
 	} else if (status == EFI_NOT_FOUND) {
 		status = efi_load_initrd_cmdline(image, &initrd, soft_limit,
 						 hard_limit);