signrom.sh has multiple bugs:
- the last byte is considered when calculating the existing checksum, but not
when computing the correction
- apprently the 'expr' expression overflows and produces incorrect results with
larger roms
- if the checksum happened to be zero, we calculated the correction byte to be
256
Instead of rewriting this in half a line of python, this patch fixes the bugs.
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
pc-bios/optionrom/signrom.sh | 7 +++----
1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/pc-bios/optionrom/signrom.sh b/pc-bios/optionrom/signrom.sh
index 975b27d..9dc5c63 100755
--- a/pc-bios/optionrom/signrom.sh
+++ b/pc-bios/optionrom/signrom.sh
@@ -31,14 +31,13 @@ x=`dd if="$1" bs=1 count=1 skip=2 2>/dev/null | od -t u1 -A n`
size=$(( $x * 512 - 1 ))
# now get the checksum
-nums=`od -A n -t u1 -v "$1"`
+nums=`od -A n -t u1 -v -N $size "$1"`
for i in ${nums}; do
# add each byte's value to sum
- sum=`expr $sum + $i`
+ sum=`expr \( $sum + $i \) % 256`
done
-sum=$(( $sum % 256 ))
-sum=$(( 256 - $sum ))
+sum=$(( (256 - $sum) % 256 ))
sum_octal=$( printf "%o" $sum )
# and write the output file
--
1.7.3.1
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