tree f4212c5aa7fc315f53beea41cc5d72bc1f4530a5
parent 8dacf6a84e9e8f7ebf27c0ca9e33aacd7506f149
author Andrew Jeffery <andrew@aj.id.au> 1627908502 +0930
committer Andrew Jeffery <andrew@aj.id.au> 1627908502 +0930

FruUtils: Rework calculateChecksum() implementation

FRU areas are sized by a single-byte count field in units of FRU blocks,
which are 8 bytes in size. As such, it's possible for a FRU area to be
up to 255 * 8 or 2040 bytes in size. An accumulation of values over such
an area to calculate the checksum can produce values exceeding 256. In
such a circumstance the current checksum implementation will mask a
negative value, invoking undefined behaviour.

Instead, accumulate into an unsigned, 8-bit type to avoid negative
masking through well-defined wrap behaviour.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ie85894004f1048413cddc62d68dd0b7ae8f6f541