1 files changed, 53 insertions, 0 deletions
diff --git a/scripts/signrom.py b/scripts/signrom.py
new file mode 100755
index 000000000..43693dba5
--- /dev/null
+++ b/scripts/signrom.py
@@ -0,0 +1,53 @@
+#!/usr/bin/env python3
+
+#
+# Option ROM signing utility
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2 or later.
+# See the COPYING file in the top-level directory.
+
+import sys
+import struct
+
+if len(sys.argv) < 3:
+    print('usage: signrom.py input output')
+    sys.exit(1)
+
+fin = open(sys.argv[1], 'rb')
+fout = open(sys.argv[2], 'wb')
+
+magic = fin.read(2)
+if magic != b'\x55\xaa':
+    sys.exit("%s: option ROM does not begin with magic 55 aa" % sys.argv[1])
+
+size_byte = ord(fin.read(1))
+fin.seek(0)
+data = fin.read()
+
+size = size_byte * 512
+if len(data) > size:
+    sys.stderr.write('error: ROM is too large (%d > %d)\n' % (len(data), size))
+    sys.exit(1)
+elif len(data) < size:
+    # Add padding if necessary, rounding the whole input to a multiple of
+    # 512 bytes according to the third byte of the input.
+    # size-1 because a final byte is added below to store the checksum.
+    data = data.ljust(size-1, b'\0')
+else:
+    if ord(data[-1:]) != 0:
+        sys.stderr.write('WARNING: ROM includes nonzero checksum\n')
+    data = data[:size-1]
+
+fout.write(data)
+
+checksum = 0
+for b in data:
+    checksum = (checksum - b) & 255
+
+fout.write(struct.pack('B', checksum))
+
+fin.close()
+fout.close()