cr50: add vendor command for retrieving flash elog

We want to be able to retrieve flash log contents using the vendor
command channel.

The input parameter of the command is the timestamp of the last
retrieved log event, or zero of the AP wants to start over.

The response is the next entry after the one requested by the AP, or
an empty message if there are no newer log messages.

BRANCH=cr50, cr50-mp
BUG=b:63760920
TEST=with the upcoming gsctools changes observed the ability to
     retrieve flash log messages.

Change-Id: I7a5438daab780c80f77cc7ebda5b719814b46489
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1525146
Reviewed-by: Namyoon Woo <namyoon@chromium.org>

1 files changed, 24 insertions, 17 deletions

diff --git a/include/tpm_vendor_cmds.h b/include/tpm_vendor_cmds.h
index 9c344d6f55..62db64e82a 100644
--- a/include/tpm_vendor_cmds.h
+++ b/include/tpm_vendor_cmds.h
@@ -134,7 +134,22 @@ enum vendor_cmd_cc {
 	LAST_VENDOR_COMMAND = 65535,
 };
 
-/* Error codes reported by extension and vendor commands. */
+/*
+ * Error codes reported by extension and vendor commands.
+ *
+ * As defined by the TPM2 spec, the TPM response code is all zero for success,
+ * and errors are a little complicated:
+ *
+ *   Bits 31:12 must be zero.
+ *
+ *   Bit 11     S=0   Error
+ *   Bit 10     T=1   Vendor defined response code
+ *   Bit  9     r=0   reserved
+ *   Bit  8     V=1   Conforms to TPMv2 spec
+ *   Bit  7     F=0   Confirms to Table 14, Format-Zero Response Codes
+ *   Bits 6:0   num   128 possible failure reasons
+ */
+
 enum vendor_cmd_rc {
 	/* EXTENSION_HASH error codes */
 	/* Attempt to start a session on an active handle. */
@@ -156,8 +171,15 @@ enum vendor_cmd_rc {
 	VENDOR_RC_IN_PROGRESS = 9,
 	VENDOR_RC_PASSWORD_REQUIRED = 10,
 
-	/* Only 7 bits available; max is 127 */
+	/* Maximum possible failure reason. */
 	VENDOR_RC_NO_SUCH_COMMAND = 127,
+
+	/*
+	 * Bits 10 and 8 set, this is to be ORed with the rest of the error
+	 * values to make the combined value compliant with the spec
+	 * requirements.
+	 */
+	VENDOR_RC_ERR = 0x500,
 };
 
 /*
@@ -172,21 +194,6 @@ enum vendor_cmd_rc {
 /* Our vendor-specific command codes go here */
 #define TPM_CC_VENDOR_CR50         0x0000
 
-/*
- * The TPM response code is all zero for success.
- * Errors are a little complicated:
- *
- *   Bits 31:12 must be zero.
- *
- *   Bit 11     S=0   Error
- *   Bit 10     T=1   Vendor defined response code
- *   Bit  9     r=0   reserved
- *   Bit  8     V=1   Conforms to TPMv2 spec
- *   Bit  7     F=0   Confirms to Table 14, Format-Zero Response Codes
- *   Bits 6:0   num   128 possible failure reasons
- */
-#define VENDOR_RC_ERR 0x00000500
-
 /*** Structures and constants for VENDOR_CC_SPI_HASH ***/
 
 enum vendor_cc_spi_hash_request_subcmd {