[PATCH v2] efi_loader: fix FinalEvents table if an EFI app invoked GetEventLog

[Ilias Apalodimas]

As described in the TCG spec [1] in sections 7.1.1 and 7.1.2 the FinalEvent
table should include events after GetEventLog has been called.  This
currently works for us as long as the kernel is the only EFI application
calling that.  Specifically we only implement what's described in 7.1.1.

So refactor the code a bit and support EFI application(s) calling
GetEventLog.  Events will now be logged in both the EventLog and FinalEvent
table as long as ExitBootServices haven't been invoked.

[1] https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev13-160330final.pdf

Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
changes since v1:
- added documentation for the internal eventlog management struct
 lib/efi_loader/efi_tcg2.c | 99 +++++++++++++++++++++++++++------------
 1 file changed, 70 insertions(+), 29 deletions(-)

diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index 189e4a5ba59c..9a36ba0f1568 100644
--- a/lib/efi_loader/efi_tcg2.c
+++ b/lib/efi_loader/efi_tcg2.c
@@ -27,6 +27,16 @@
 #include <linux/unaligned/generic.h>
 #include <hexdump.h>
 
+/* internal eventlog management struct
+ *
+ * @buffer:		eventlog buffer
+ * @final_buffer:	finalevent config table buffer
+ * @pos:		current position of 'buffer'
+ * @final_pos:		current position of 'final_buffer'
+ * @get_event_called:	true if GetEventLog has been invoked at least once
+ * @ebs_called:		true if ExitBootServices has been invoked
+ * @truncated:		true if the 'buffer' is truncated
+ */
 struct event_log_buffer {
 	void *buffer;
 	void *final_buffer;
@@ -34,6 +44,7 @@ struct event_log_buffer {
 	size_t final_pos; /* final events config table position */
 	size_t last_event_size;
 	bool get_event_called;
+	bool ebs_called;
 	bool truncated;
 };
 
@@ -186,39 +197,29 @@ static efi_status_t tcg2_pcr_extend(struct udevice *dev, u32 pcr_index,
 	return EFI_SUCCESS;
 }
 
-/* tcg2_agile_log_append - Append an agile event to out eventlog
+/* put_event - Append an agile event to an eventlog
  *
  * @pcr_index:		PCR index
  * @event_type:		type of event added
  * @digest_list:	list of digest algorithms to add
  * @size:		size of event
  * @event:		event to add
+ * @log:		log buffer to append the event
  *
- * @Return: status code
  */
-static efi_status_t tcg2_agile_log_append(u32 pcr_index, u32 event_type,
-					  struct tpml_digest_values *digest_list,
-					  u32 size, u8 event[])
+static void put_event(u32 pcr_index, u32 event_type,
+		      struct tpml_digest_values *digest_list, u32 size,
+		      u8 event[], void *log)
 {
-	void *log = (void *)((uintptr_t)event_log.buffer + event_log.pos);
 	size_t pos;
 	size_t i;
 	u32 event_size;
 
-	if (event_log.get_event_called)
-		log = (void *)((uintptr_t)event_log.final_buffer +
-			       event_log.final_pos);
-
 	/*
 	 * size refers to the length of event[] only, we need to check against
 	 * the final tcg_pcr_event2 size
 	 */
 	event_size = size + tcg_event_final_size(digest_list);
-	if (event_log.pos + event_size > TPM2_EVENT_LOG_SIZE ||
-	    event_log.final_pos + event_size > TPM2_EVENT_LOG_SIZE) {
-		event_log.truncated = true;
-		return EFI_VOLUME_FULL;
-	}
 
 	put_unaligned_le32(pcr_index, log);
 	pos = offsetof(struct tcg_pcr_event2, event_type);
@@ -242,25 +243,63 @@ static efi_status_t tcg2_agile_log_append(u32 pcr_index, u32 event_type,
 	memcpy((void *)((uintptr_t)log + pos), event, size);
 	pos += size;
 
-	/* make sure the calculated buffer is what we checked against */
+	/*
+	 * make sure the calculated buffer is what we checked against
+	 * This check should never fail.  It checks the code above is
+	 * calculating the right length for the event we are adding
+	 * */
 	if (pos != event_size)
-		return EFI_INVALID_PARAMETER;
+		log_err("Appending to the EventLog failed\n");
 
-	/* if GetEventLog hasn't been called update the normal log */
-	if (!event_log.get_event_called) {
-		event_log.pos += pos;
-		event_log.last_event_size = pos;
-	} else {
-	/* if GetEventLog has been called update config table log */
-		struct efi_tcg2_final_events_table *final_event;
+}
 
-		final_event =
-			(struct efi_tcg2_final_events_table *)(event_log.final_buffer);
-		final_event->number_of_events++;
-		event_log.final_pos += pos;
+/* tcg2_agile_log_append - Append an agile event to an eventlog
+ *
+ * @pcr_index:		PCR index
+ * @event_type:		type of event added
+ * @digest_list:	list of digest algorithms to add
+ * @size:		size of event
+ * @event:		event to add
+ * @log:		log buffer to append the event
+ *
+ * @Return: status code
+ */
+static efi_status_t tcg2_agile_log_append(u32 pcr_index, u32 event_type,
+					  struct tpml_digest_values *digest_list,
+					  u32 size, u8 event[])
+{
+	void *log = (void *)((uintptr_t)event_log.buffer + event_log.pos);
+	u32 event_size = size + tcg_event_final_size(digest_list);
+	struct efi_tcg2_final_events_table *final_event;
+	efi_status_t ret = EFI_SUCCESS;
+
+	/* if ExitBootServices hasn't been called update the normal log */
+	if (!event_log.ebs_called) {
+		if (event_log.truncated ||
+		    event_log.pos + event_size > TPM2_EVENT_LOG_SIZE) {
+			event_log.truncated = true;
+			return EFI_VOLUME_FULL;
+		}
+		put_event(pcr_index, event_type, digest_list, size, event, log);
+		event_log.pos += event_size;
+		event_log.last_event_size = event_size;
 	}
 
-	return EFI_SUCCESS;
+	if (!event_log.get_event_called)
+		return ret;
+
+	/* if GetEventLog has been called update FinalEventLog as well */
+	if (event_log.final_pos + event_size > TPM2_EVENT_LOG_SIZE)
+		return EFI_VOLUME_FULL;
+
+	log = (void *)((uintptr_t)event_log.final_buffer + event_log.final_pos);
+	put_event(pcr_index, event_type, digest_list, size, event, log);
+
+	final_event = event_log.final_buffer;
+	final_event->number_of_events++;
+	event_log.final_pos += event_size;
+
+	return ret;
 }
 
 /**
@@ -1303,6 +1342,7 @@ static efi_status_t efi_init_event_log(void)
 	event_log.pos = 0;
 	event_log.last_event_size = 0;
 	event_log.get_event_called = false;
+	event_log.ebs_called = false;
 	event_log.truncated = false;
 
 	/*
@@ -1792,6 +1832,7 @@ efi_tcg2_notify_exit_boot_services(struct efi_event *event, void *context)
 
 	EFI_ENTRY("%p, %p", event, context);
 
+	event_log.ebs_called = true;
 	ret = platform_get_tpm2_device(&dev);
 	if (ret != EFI_SUCCESS)
 		goto out;
-- 
2.33.1