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[int13] Avoid potential division by zero 

Avoid using a zero sector count to guess the disk geometry, since that
would result in a division by zero when calculating the number of
cylinders.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/58/merge
Michael Brown 2017-01-26 09:31:40 +00:00
parent f3ba0fb5fd
commit fcf7751565
1 changed files with 7 additions and 3 deletions
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10
src/arch/x86/interface/pcbios/int13.c
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@ -561,6 +561,8 @@ static int int13_guess_geometry_hdd ( struct int13_drive *int13, void *scratch,
struct master_boot_record *mbr = scratch;
struct partition_table_entry *partition;
unsigned int i;
unsigned int end_head;
unsigned int end_sector;
int rc;
/* Default guess is xx/255/63 */
@ -586,10 +588,12 @@ static int int13_guess_geometry_hdd ( struct int13_drive *int13, void *scratch,
*/
for ( i = 0 ; i < 4 ; i++ ) {
partition = &mbr->partitions[i];
if ( ! partition->type )
end_head = PART_HEAD ( partition->chs_end );
end_sector = PART_SECTOR ( partition->chs_end );
if ( ! ( partition->type && end_head && end_sector ) )
continue;
*heads = ( PART_HEAD ( partition->chs_end ) + 1 );
*sectors = PART_SECTOR ( partition->chs_end );
*heads = ( end_head + 1 );
*sectors = end_sector;
DBGC ( int13, "INT13 drive %02x guessing C/H/S xx/%d/%d based "
"on partition %d\n",
int13->drive, *heads, *sectors, ( i + 1 ) );