security/tpm/tspi: Set return type of tcpa_log_add_table_entry as void

Change f849972 (security/vboot: Enable TCPA log extension) enabled
support for adding TCPA log to CBMEM. However, if CBMEM is not online,
this function doesn't do anything and returns early. This condition is
not really a valid error condition as it depends on when the call to
tcpa_log_add_table_entry is made. Since tcpa_log_add_table_entry
returns -1 when cbmem is not online, tpm_extend_pcr prints an error
message with prefix "ERROR:". This can confuse any scripts trying to
catch errors in boot flow.

This CL makes the following changes:
1. Removes the print in tpm_extend_pcr since tcpa_log_add_table_entry
already prints out appropriate ERROR messages in case of failure to
add log entry.
2. Since the return value of tcpa_log_add_table_entry is not used
anymore, return type for tcpa_log_add_table_entry is changed to void.

BUG=b:112030232

Change-Id: I32d313609a3e57845e67059b3747b81b5c8adb2a
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/27757
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-by: Justin TerAvest <teravest@chromium.org>

src/security/tpm/tspi.h

@@ -28,8 +28,9 @@ void tcpa_log_init(void);
 /**
  * Add table entry for cbmem TCPA log.
  */
-int tcpa_log_add_table_entry(const char *name, const uint32_t pcr,
-			     const uint8_t *digest, const size_t digest_length);
+void tcpa_log_add_table_entry(const char *name, const uint32_t pcr,
+			      const uint8_t *digest,
+			      const size_t digest_length);
 
 /**
  * Ask vboot for a digest and extend a TPM PCR with it.

src/security/tpm/tspi/log.c

@@ -44,24 +44,24 @@ void tcpa_log_init(void)
 	printk(BIOS_DEBUG, "TCPA log created at %p\n", tclt);
 }
 
-int tcpa_log_add_table_entry(const char *name, const uint32_t pcr,
+void tcpa_log_add_table_entry(const char *name, const uint32_t pcr,
 			      const uint8_t *digest, const size_t digest_length)
 {
 	MAYBE_STATIC struct tcpa_table *tclt = NULL;
 	struct tcpa_entry *tce;
 
 	if (!cbmem_possibly_online())
-		return -1;
+		return;
 
 	tclt = cbmem_find(CBMEM_ID_TCPA_LOG);
 	if (!tclt) {
 		printk(BIOS_ERR, "ERROR: No TCPA log table found\n");
-		return -1;
+		return;
 	}
 
 	if (tclt->num_entries == tclt->max_entries) {
 		printk(BIOS_WARNING, "ERROR: TCPA log table is full\n");
-		return -1;
+		return;
 	}
 
 	tce = &tclt->entries[tclt->num_entries++];
@@ -70,6 +70,4 @@ int tcpa_log_add_table_entry(const char *name, const uint32_t pcr,
 	tce->pcr = pcr;
 	memcpy(tce->digest, digest, digest_length);
 	tce->digest_length = digest_length;
-
-	return 0;
 }

src/security/tpm/tspi/tspi.c

@@ -190,9 +190,7 @@ uint32_t tpm_extend_pcr(int pcr, uint8_t *digest,
 	if (result != TPM_SUCCESS)
 		return result;
 
-	result = tcpa_log_add_table_entry(name, pcr, digest, digest_len);
-	if (result != 0)
-		printk(BIOS_ERR, "ERROR: Couldn't create TCPA log entry\n");
+	tcpa_log_add_table_entry(name, pcr, digest, digest_len);
 
-	return 0;
+	return TPM_SUCCESS;
 }