[build] Fix signed/unsigned division in util/zbin.c

Commit b149a99 ([build] Round up SUBx deltas) introduced a
signed/unsigned issue that affects gPXE images built on 32-bit hosts.
The zbin fixup utility performed an unsigned division, which led to
.usb images with an incorrect number of sectors to load.

The issue snuck by on 64-bit hosts since uint32_t is promoted to long.
On 32-bit hosts it is promoted to unsigned long.

Modified-by: Michael Brown <mcb30@etherboot.org>
Signed-off-by: Michael Brown <mcb30@etherboot.org>

diff --git a/src/util/zbin.c b/src/util/zbin.c
index d4eebe5..1513289 100644 (file)
--- a/src/util/zbin.c
+++ b/src/util/zbin.c
@@ -213,7 +213,8 @@ static int process_zinfo_subtract ( struct input_file *input,
                                    size_t datasize ) {
        size_t offset = subtract->offset;
        void *target;
-       long delta;
+       signed long raw_delta;
+       signed long delta;
        unsigned long old;
        unsigned long new;
 
@@ -224,9 +225,9 @@ static int process_zinfo_subtract ( struct input_file *input,
        }
 
        target = ( output->buf + offset );
-       delta = ( ( align ( output->len, subtract->divisor ) -
-                   align ( input->len, subtract->divisor ) )
-                 / subtract->divisor );
+       raw_delta = ( align ( output->len, subtract->divisor ) -
+                     align ( input->len, subtract->divisor ) );
+       delta = ( raw_delta / ( ( signed long ) subtract->divisor ) );
 
        switch ( datasize ) {
        case 1: {