ap_ro_hash.py: improve error processing and help messages

This patch adds processing of the case when the Cr50 does not support
the vendor command setting the AP RO areas hash.

Also improve help message and include text descriptions of the
encountered errors, if any.

BUG=b:153764696
TEST=with the rest of the patches applied verified that programming of
     the AP RO verification space succeeds when expected, and proper
     errors are reported in case of failure.

     ./util/test_ap_ro_hash.py also still succeeds.

Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Change-Id: Ie3898ef5ab925404decd730f457267615c9ab39c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2171397
Reviewed-by: Andrey Pronin <apronin@chromium.org>

1 files changed, 30 insertions, 5 deletions

diff --git a/util/ap_ro_hash.py b/util/ap_ro_hash.py
index a6a8fc2837..2961a51f1f 100755
--- a/util/ap_ro_hash.py
+++ b/util/ap_ro_hash.py
@@ -62,6 +62,9 @@ class ApRoTpmResponseError(Exception):
 
 VENDOR_CC_SEED_AP_RO_CHECK = 54
 
+# Code returned by Cr50 if a vendor command is not supported.
+VENDOR_RC_NO_SUCH_COMMAND_ERROR = 0x57f
+
 # The tag and format are the same for command and response.
 TPM_TAG = 0x8001
 HEADER_FMT = '>H2LH'
@@ -347,9 +350,10 @@ def send_to_cr50(ranges, digest):
     channel = TpmChannel()
     channel.write(p.packet())
     tpm_response = Cr50TpmResponse(channel.read(), subcmd)
-    if tpm_response.rc:
+    # Return payload value if present, if not - the header RC value.
+    if tpm_response.payload:
         return int(tpm_response.payload[0])
-    return 0
+    return tpm_response.rc
 
 
 def read_fmap(tmpd):
@@ -476,14 +480,20 @@ def calculate_hash(ro_file, ranges):
     return sha256.digest()
 
 
+usage_str = """
+%s: [-v] <range>|<fmap_area> [<range>|<fmap_area>...]
+         <range>: two colon separated hex values, AP flash area offset and size
+         <fmap_area>: symbolic name of the area as reported by dump_fmap
+         All ranges and fmap areas must fit into the WP_RO FMAP area
+"""  % sys.argv[0].split('/')[-1]
+
 def get_args(args):
     """Prepare argument parser and retrieve command line arguments.
 
     Returns the parser object with a namespace with all present optional
     arguments set.
     """
-    parser = argparse.ArgumentParser(description='AP RO Hashing utility')
-
+    parser = argparse.ArgumentParser(usage=usage_str)
     parser.add_argument(
         '--verbose', '-v',
         type=bool,
@@ -496,6 +506,17 @@ def get_args(args):
 def main(args):
     'Main function, receives a list of strings, command line arguments'
 
+    # Map of possible error codes returned by Cr50 (both vendor command and
+    # subcommand level errors) into strings.
+    error_codes = {
+        1 : 'Vendor command too short',
+        2 : 'Vendor command size mismatch',
+        3 : 'Bad offset value',
+        4 : 'Bad range size',
+        5 : 'Already programmed',
+        VENDOR_RC_NO_SUCH_COMMAND_ERROR : 'Insufficient C50 version',
+    }
+
     nsp, rest = get_args(args)
 
     if nsp.verbose:
@@ -548,7 +569,11 @@ def main(args):
 
     rv = send_to_cr50(ranges, digest)
     if rv != 0:
-        LOG.error('Cr50 returned error %d' % rv)
+        err_str = error_codes.get(rv, 'Unknown')
+        LOG.error('Cr50 returned %s%x (%s)' % (
+            # Add 0x prefix if value exceeds 9.
+            '0x' if rv > 9 else '',
+            rv, err_str))
         return rv
     print('SUCCEEDED')
     return 0